Town of Leland Street Design Guidelines

Transcription

1 Town of Leland Street Design Guidelines Prepared for: Town of Leland February 2018

2 Table of Contents 1 Introduction Street Network Plans and Policies Relevant Plans and Policies Complete Streets Street Typologies and Characteristics Types and Roles of Streets Flexcode Street Typology Conventional Subdivision Street Typology Street Design Overview Street Design Principles Cross-Section Elements Streetscape Travelway or Shared Vehicle Zone Standard Cross-Sections Flexcode Thoroughfare Cross-Sections Conventional Subdivision Cross-Sections Planning and Design Guidelines Design Vehicles Design Speed Access Management Offset Driveways Driveway and Intersection Spacing Designing Streets for Transit Access to Transit Bus Stop Design Elements Bus Stop Placement i

3 6.4.4 Bus Pull-Outs versus In-Lane Stops Example Bus Stop Guidance Other Geometric Design Elements Vertical Alignment Horizontal Alignment Sight Distance Horizontal Clearance/Clear Zone Designing to Moderate Traffic Speeds Intersection Design Principles of Intersection Design Intersection Geometry Intersection Skew Corner Radii Curb Extensions Crosswalk and Ramp Placement On-Street Praking Near Intersections Right-Turn Channelization Islands Roundabouts Advantages and Disadvantages General Design Elements of Roundabouts Roundabout Design Criteria Pedestrian Crossings Principles of Pedestrian Crossing Design High-Visibility Crosswalks Advanced Yield/Stop Lines Curb Extensions Lighting Bicycle Facilities Principles of Bicycle Facility Design Integrating Bicycles into the Street System Bicycle Boulevards...85 ii

4 9 Streetscape Stormwater Management Goals and Benefits of Stormwater Management Principles of Stormwater Management Definitions Tools for Stormwater Management Street Furniture and Amenities Utilities Location Design Guidelines Process Street Trees and Plantings Street Trees Understory Landscaping Lighting Acknowledgments iii

5 List of Tables Table 1. Flexcode typology...8 Table 2. Conventional Subdivision (CSD) typology Table 3. Recommended driveway and intersection spacing (Flexcode) Table 4. Recommended driveway and intersection spacing (CSD) Table 5. Bus stop placement considerations List of Figures Figure 1. Access versus mobility by facility type...7 Figure 2. Adding medians and consolidating driveways to manage access Figure 3. Corner with many wide driveways (left) and reconstructed corner with fewer, narrower driveways (right) Figure 4. Driveway offsets Figure 5. ADA compliant bus stop Figure 6. Hierarchy of bus stop amenities Figure 7. Realigning a skewed intersection (left) to a right-angle connection (right) results in less exposure distance and better visibility for all users Figure 8. Tighter corner radii reduce crossing distance and slow turning traffic..64 Figure 9. The effective corner radius controls turning speeds and the ability of large vehicles to turn Figure 10. Corner radii can be kept smaller by allowing trucks and buses to turn into multiple receiving lanes Figure 11. Curb extensions improve sight distance between pedestrians and motorists, possibly allowing additional on-street parking iv

6 Figure 12. One curb ramp per crosswalk should be provided at corners. Ramps should align with sidewalks and crosswalks Figure 13. Traffic channelization is an effective mitigation strategy when intersection radii reduction is not an option Figure 14. Sharper angles of slip lanes are important to slow cars and increase visibility Figure 15. Single-lane roundabout Figure 16. Curb extensions and median make crossing four-lane streets safer and more manageable Figure 17. Longitudinal crosswalk markings are more visible than lateral crosswalk markings Figure 18. Typical crosswalk markings: Continental, Ladder, and Staggered Continental Figure 19. Example of staggered continental crosswalk Figure 20. Advanced yield markings Figure 21. Example of advanced yield markings Figure 22. Curb extensions Figure 23. Example of curb extensions Figure 24. Proper placement of crosswalk illumination Figure 25. Rain garden detail Figure 26. Infiltration trench v

7 1 Introduction This document has been developed to guide the design of new streets within the Town of Leland, as well as for improvements to existing streets. The primary goal of these Guidelines is to coordinate public and private development in creating an integrated, efficient, sustainable, cost-effective system of transportation infrastructure that serves and protects the entire community s health, economic vitality, cultural resources, and natural environment. A key objective is to minimize disruption, conflict, uncertainty, and unnecessary expense as the Town of Leland grows and evolves over the long term. These Guidelines are intended to supplement existing policies, rather than replace them. In fact, the development of Street Design Guidelines is a recommendation in the Town s adopted Master Plan. Street Design Guidelines also support land use and other ordinances and regulations of the Town of Leland. Applicable ordinances and regulations will prevail in the case of any conflicts with these Guidelines. Certain projects relying on State and Federal funding may be subject to regulations and standards that differ from the guidance provided in this document. In such cases, those regulations and standards may subordinate elements of these Guidelines. Town of Leland staff will apply fundamental principles and practices of engineering and planning in evaluating design and construction plans to which these Guidelines may apply. While the guidance in this document can apply to both existing and new streets, the design and construction of new streets is the focus of this effort. Retrofitting existing streets is complicated by right-of-way and other constraints; resulting disruptions and expense may be difficult to justify. 1 Introduction

8 A significant challenge in developing and presenting these Guidelines is the need to address two sets of subdivision standards, one based on conventional subdivision (CSD) zoning, and one based on the newer transect-based Flexcode. Every effort has been made to provide guidance that is flexible enough to address the most likely scenarios without becoming too complicated or difficult to understand and apply. To avoid redundancy and to reduce the length of this document, guidelines and specifications provided in other applicable plans, codes, or guidance documents are included by reference in these Guidelines whenever practical. This approach should also reduce the need for revisions to this document due to changes or updates in the referenced materials. This document should not be considered static or final. These Guidelines should be revisited and revised as needed to remain relevant and consistent with the growing Town of Leland, as well as the ever-evolving state of the practice. In particular, the pending development and implementation of a Uniform Design Ordinance (UDO) will require careful coordination with the Street Design Guidelines, and revisions are to be expected. Some portions of these Guidelines are more suggestive than prescriptive in nature, with the goal of identifying productive areas for further study and refinement. For example, the portion of these Guidelines dealing with streetscape elements (Section 9), is more general in nature than the preceding sections addressing roadway design. Other topics that could be addressed in future revisions or supplements could include traffic calming and wayfinding. The guidance presented in this document is derived from widely-accepted sources, including: AASHTO Policy on Geometric Design of Highways and Streets (the Green Book ) AASHTO Policy on the Geometric Design of Highways and Streets AASHTO Guide for the Development of Bicycle Facilities FHWA/USDOT Flexibility in Highway Design NCDOT Complete Streets Planning and Design Guidelines NCDOT Roadway Design Manual FHWA Manual on Uniform Traffic Control Devices (MUTCD) NCDOT Traditional Neighborhood Development Street Design Guidelines ITE/CNU Designing Walkable Urban Thoroughfares: A Context Sensitive Approach NACTO Urban Street Design Guide NACTO Transit Street Design Guide Los Angeles County Model Design Manual for Living Streets 2 Introduction

9 2 Street Network Plans and Policies 2.1 Relevant Plans and Policies Several existing policies of the Town of Leland relating to land use development and the design and construction of streets should be carefully considered when employing these Guidelines. The Town of Leland maintains both Flexcode and conventional zoning based subdivision standards, requiring Street Design Guidelines that address both situations without becoming overly complex and unwieldy. Flexcode Article 1. General to All Plans includes descriptions of each Transect Zone (T) and a table summarizing which types of Flexcode Thoroughfares are permitted in each Transect Zone. Article 3. Public Works addresses vehicular and pedestrian traffic, vehicular lanes, and public frontages in Sections and Key elements include: Lane widths, turning radii, and target speeds for Thoroughfares within each Transect Zone Vehicular Lane and Parking Assemblies for allowable combinations of Thoroughfare Types and Transect Zones General and Specific Public Frontages for various Thoroughfares and Transect Zones Appropriate plantings for allowable combinations of Thoroughfare Types and Transect Zones Appropriate types of light fixtures for each Transect Zone Article 7. Definitions of Terms defines a number of relevant terms, including seven Thoroughfare Types plus specific cross-section and streetscape elements. 3 Street Network Plans and Policies

10 Chapter 22 of the Code of Ordinances addresses Subdivision Regulations, which cover topics such as: Categories of streets and associated design standards Right-of -way Connectivity Parking requirements Sidewalks and bicycle facilities Private streets Water and sanitary sewer systems, as well as stormwater Street lighting There are other relevant policy, planning, and design resources that should be examined to provide additional context regarding existing and anticipated development, and to address specific design considerations. Leland Master Plan Leland Pedestrian Plan Comprehensive Bicycle Plan for Leland Connecting Northern Brunswick County (Collector Street Plan) Cape Fear Transportation 2040 Metropolitan Transportation Plan WMPO Comprehensive Transportation Plan Approved or adopted roadway or corridor plans Leland Capital Improvement Plan and authorized roadway projects ADA Standards for Accessible Design These guidelines are intended to advance the implementation of recommendations from the above plans, and from future updates to these and other plans. Specifically, the cross-sections presented in this document can be applied to local, collector, and some minor arterial streets identified in the listed plans. Similarly, bicycle and pedestrian plan recommendations can be implemented in accordance with the appropriate design elements described in the Street Design Guidelines. Recommendations in these Guidelines are consistent with ADA Standards for Accessible Design; however, it may be necessary to consult the ADA Standards for details of particular treatments, and to ensure that the latest and most appropriate designs are employed. 2.2 Complete Streets As defined by the National Complete Streets Coalition, Complete streets are designed and operated to enable safe access for all users. Pedestrians, 4 Street Network Plans and Policies

11 bicyclists, motorists and transit riders of all ages and abilities must be able to safely move along and across a complete street. The North Carolina Board of Transportation adopted a Complete Streets policy in 2009, directing NCDOT to: consider and incorporate all modes of transportation when building new projects or making improvements to existing infrastructure. Under the new policy, NCDOT will collaborate with cities, towns, and communities during the planning and design phases of new streets or improvement projects. Together, they will decide how to provide the transportation options needed to serve the community and complement the context of the area. Furthermore: [A] complete streets philosophy means that NCDOT and its partners will provide a network of streets that safely and comfortably accommodate all users, including bicyclists, pedestrians, and transit users. Typical elements that make up a complete street include sidewalks, bicycle lanes, appropriate street widths and speeds, and transit stops with benches, shelters, and access points that comply with Americans with Disabilities Act requirements. Complete street design elements that emphasize safety, mobility, and accessibility for those using a variety of travel modes may also include crosswalks, bus lanes, adequate separation between sidewalks and streets, street trees and other landscaping, lighting, and signal systems. Though complete streets may initially be designed or built as apparently disconnected segments, the intent is to incrementally grow and develop extensive networks of complete streets. This will require systematic application of the complete streets principles and designs included in these guidelines. Recognizing that implementing Complete Streets policies can make an important contribution to the quality of life in the Town of Leland, this guidance presents two comprehensive sets of street typologies, one for Flexcode application, and one for conventional subdivisions. Both are intended to address the needs and limitations of all users. Given the range of land uses and transportation functions to be accommodated, some flexibility is required to allow variation from the principles of Complete Streets, and from NCDOT s Complete Streets Policy. This is especially true given the that the Town of Leland maintains both Flexcode and conventional subdivision standards. While the recommended street typologies adhere to the principles of Complete Streets, some recommended cross-sections and design features place more emphasis on moving vehicular traffic than others. Land-use context, roadway function, and frontage type must be considered in balancing the often-competing objectives of moving traffic versus supporting alternate modes of travel. 5 Street Network Plans and Policies

12 3 Street Typologies and Characteristics 3.1 Types and Roles of Streets The Federal Highway Function and Classification system is the conventional classification system typically used to define the function and operational requirements for streets. These classifications are also used as the primary basis for geometric design criteria. A key principle behind the functional classification system is the need to satisfy the essential but competing roles played by all roads: mobility and access. Higher-level roads (arterials, expressways, freeways) maximize traffic throughput, or mobility. These facilities carry higher volumes of traffic at higher speeds. They tend to serve longer trips, and have fewer access points. Trucks comprise a larger proportion of traffic. At the other end of the spectrum, local streets carry lower volumes of traffic at lower speeds. They serve more short trips, and provide frequent and convenient access to adjacent land uses. Pedestrian and bicycle activity tends to be higher on these streets, and large trucks are infrequent. Collector streets fall in the continuum between these two extremes, and must balance mobility and access needs based on the surrounding land use and transportation network. Figure 1 compares different road types by mobility and access. Traffic volume, trip characteristics, speed and level of service, and other factors in the functional classification system relate to the mobility of motor vehicles, not bicyclists or pedestrians, and do not consider the context or land use of the surrounding environment. This approach, while appropriate for high speed rural and some suburban roadways, does not provide designers with guidance on how to design for Complete Streets, or in a contextsensitive manner. 6 Street Typologies and Characteristics

13 Arterials Mobility Land Access Collectors Locals Proportion of Service Figure 1. Access versus mobility by facility type. (Adapted from FHWA Office of Highway Policy Information) The street types described in these Guidelines balance mobility among all transportation modes, placing a greater emphasis on pedestrians and bicycles where appropriate. The functional classification system can be generally applied to the street types in this document, as suggested in Tables 1 and 2. Designers should recognize the need for greater flexibility in applying design criteria, based more heavily on context and the need to create a safe environment for pedestrians and bicyclists, rather than strictly following the conventional application of functional classification in determining geometric criteria. The two street typologies developed for these Guidelines attempt to reconcile the presence of both conventional and Flexcode zoning based standards in Leland. Section 4 presents more detailed explanations of the function and design elements of each, as well as typical cross-sections and dimensions. These cross-sections and their dimensions must be considered in context, and appropriate deviations may be approved. It should be noted that neither street typology includes all possible street categories, focusing instead on those most typical of urban/suburban residential and mixed-use subdivisions. Rural and higher-level streets are not addressed in detail. Given rapid urbanization, most streets falling under these Guidelines will be local or collector streets constructed as part of a 7 Street Typologies and Characteristics

14 subdivision. Most new higher-level and rural projects will be NCDOT responsibility, as primary (US/NC) routes or other state maintained (secondary) roads. 3.2 Flexcode Street Typology The street typology developed for the Leland Flexcode is based on thoroughfare types defined in the Flexcode. These Guidelines establish cross-section and design characteristics for the following thoroughfare types. Each of these roadway types is associated with one or more Flexcode Transect Zones, reflecting differences associated with the type and density of the surrounding land use. A description of each Flexcode thoroughfare type is included on its cross-section sheet. Highway T2 Road T2 and Road T3 Street T3/T4 and Street T4O/T5 Drive T3/T4 and Drive T4O/T5 Avenue T3/T4 and Avenue T4O/T5 Commercial Street T4O/T5 Multi-way Boulevard (Angled or Parallel Parking) T4O/T5 Rear Lane T1-T4 Rear Alley T3-T5 Table 1 relates the above Flexcode thoroughfare types to the traditional Functional Classification system. Table 1. Flexcode typology. Flexcode Thoroughfares Functional Classification Road Local Street Collector Commercial Street Avenue Collector Arterial Drive Collector Parkway Multi-way Boulevard Collector Arterial Rear Lane -- Rear Alley -- Highway Collector Arterial 8 Street Typologies and Characteristics

15 3.3 Conventional Subdivision Street Typology The following street typology is intended for application under conventional subdivision standards. While there is not one-to-one correspondence, the recommended design characteristics and cross-sections within the CSD Typology are intended to be consistent with the Street Categories defined in Chapter 22 Subdivisions of the Leland Code. Local Streets Residential Yield Street R-15/R-6/PUD Residential General Street (Parallel Parking or Bike Lanes) R-15/R-6/PUD Residential Swale Street (with/without Bike Lanes) R-20/R-15/RMH Mixed-Use Streets Main Street C2 Two-Lane Avenue (Divided or Undivided) C1/MF/O&I/RMH Major Streets Four-Lane Avenue, (Parallel Parking or Divided) C1/MF/O&I/RMH Multi-way Boulevard (Angled or Parallel Parking) C2 Industrial, Service, and Access Facilities Industrial Street C3 Residential Alley All residential zones Table 2 relates the above CSD street types to the traditional Functional Classification system, and to the Street Categories defined in the Leland Code, Chapter 22: Subdivisions. 9 Street Typologies and Characteristics

16 Table 2. Conventional Subdivision (CSD) typology. CSD Typology Leland Code, Street Categories (Chapter 22 Subdivisions) Functional Classification Local Streets Mixed-Use Streets Major Streets Industrial, Service, and Access Facilities Residential Yield Street Local Street Local Residential Street Main Street Main Street Avenue Avenue Avenue Multi-way Boulevard Industrial Street N/A -- Local Residential Street Residential Collector Street Residential Collector Street Minor Thoroughfare Frontage Road Minor Thoroughfare Minor Thoroughfare Major Thoroughfare Minor Thoroughfare Major Thoroughfare Local Street Frontage Road Local Collector Collector Collector Arterial Collector Arterial Parkway Collector Arterial Collector Residential Alley Alley -- Freeway Expressway Freeway Expressway 10 Street Typologies and Characteristics

17 4 Street Design Overview Streets and their geometric design have traditionally focused on the movement of motor vehicles, resulting in street environments that may overlook other users. This emphasis can be seen in wide travel lanes, large corner radii, and turn lanes that can increase speeds through intersections, impede pedestrian safety and overall connectivity for non-automobile users. The geometric design of roadways and intersections has usually reflected the goal of moving traffic quickly, with little regard to the overall character and context of adjacent land uses. These Guidelines are intended to help achieve a reasonable balance among all travel modes with respect to safety, mobility and access. They also strive to enhance the relationship between streets and the surrounding built and natural environments. The goal of this approach is to design complete streets that yield broad, long-term value beyond the efficient movement of traffic. 4.1 Street Design Principles The following principles guide the design of a complete street: Design to accommodate all users. Street design should accommodate all users of the street, including pedestrians, bicyclists, transit users, automobiles, and commercial vehicles. A well-designed traveled way provides appropriate space for all street users to coexist. Design using the appropriate speed for the surrounding context. The right design speed should respect the desired role and responsibility (function) of the street, including the type and intensity of land use, urban form, the desired activities on the sidewalk, such as outdoor dining, and the overall safety and comfort of pedestrians and bicyclists. The speed of vehicles impacts all users of the street and the livability of the surrounding area. Lower speeds can reduce the severity of crashes and injuries. Design for safety. The safety of all street users, especially the most vulnerable users 11 Street Design Overview

18 (children, the elderly, and disabled) and modes (pedestrians and bicyclists) should be paramount in any design of the traveled way. The safety of streets can be dramatically improved through appropriate geometric design and operations. 4.2 Cross-Section Elements Street cross-sections comprise two distinct zones within the right-of-way: Streetscape and Travelway or Shared Vehicle Zone Streetscape The streetscape surrounds the travelway, defining the transition between traffic and land use. It accommodates people, whether walking, sitting, standing, or accessing other modes. The streetscape also establishes aesthetics and urban context through landscaping, furnishings, and lighting fixtures. Specific components of the streetscape zone may include: Planting Strip or Green Zone. Location for street trees and other vegetation, typically between the curb and sidewalk. Where appropriate and safe, may also include signs, benches light poles, and fire hydrants. May be hardscaped in denser urban settings, with trees in planters. Sidewalk. Paved pedestrian facility or multi-use path. Sidewalks separated from the back-of-curb are preferred due to buffering of pedestrians from traffic. Generally provided on both sides, especially when providing transit access. Sidewalk widths may vary from 6 to 12 feet, depending on street type and adjacent land use. Higher pedestrian volumes typical of urban or main street settings warrant wider sidewalks, and may allow for other activities or amenities, such as outside dining. Maintenance Strip. Space behind the sidewalk (or curb or edge-of-pavement in the absence of sidewalks) providing access for maintaining sidewalks and underground utilities. The maintenance strip represents the width of additional easement needed beyond the right-of-way to ensure an adequate clear working space. Although a 20 clear zone is ideal for major utility work, less space is needed for routine maintenance. The cross-sections recommended in this Guidance attempt to provide 20 of maintenance space outside the tree line whenever practical, but sometimes fall short when the additional easement needed creates an excessive building setback, or is otherwise inconsistent with the context and character of the street frontage Travelway or Shared Vehicle Zone The travelway is the paved width between street curbs, although certain wider cross-sections may include landscaped medians. Components found in the travelway may include: General Travel Lane. General travel lanes are designed to accommodate all types of vehicles. Lane and street widths, as well as curb radii and other geometric attributes, are determined by design parameters of the general travel lane. Travel lane widths should be determined by the desired speed within the area served by that street, as well as by environmental context and transportation function. For example, narrower travel lanes reduce traffic speeds, but large trucks, service vehicles and large transit vehicles may require wider lanes and larger turn radii. 12 Street Design Overview

19 In lower speed, urban environments, lane widths are typically measured to the curb face instead of the edge of the gutter pan. Consequently, when curb sections with gutter pans are used, vehicle, bicycle, and parking lane dimensions all include the width of the gutter pan. Shared travel lanes may be considered for bicycles when outside lanes are at least 14 feet wide travel speeds do not exceed 35 mph. Turn Lane. The need for turn lanes should be balanced between the desire to manage vehicle speeds and the potential impact of a wider travelway on the streetscape and surrounding land uses. Turn lanes can improve traffic operations and safety and may allow higher speeds to occur through intersections, since slower moving turning vehicles can move over to the turn lane, allowing the through vehicles to maintain their speed. Left-turn lanes are generally desirable in an urban environment since there are negative impacts to roadway capacity and safety when left turns block the through movement of vehicles or result in queue spillback across other intersections. The installation of a leftturn lane can be beneficial when used to perform a road diet such as repurposing a fourlane section to three lanes with the center lane providing for turning movements. Although separate right-turn lanes can benefit vehicular traffic in certain situations, they can also hinder walkability. The presence of right-turn lanes increases crossing distances for pedestrians, as well as encouraging higher travel speeds for through and turning traffic. In developments that promote multimodality, right-turn lanes should be used judiciously, and avoided if possible. Exclusive right-turn lanes should be implemented only when justified by an engineering study that considers and balances the mobility, access and safety factors. When dedicated or exclusive right-turn lanes are used, raised channelization islands should be considered to mitigate potential impacts on pedestrian movements. On-Street Parking. On-street parking can be important in the urban environment for the success of the retail businesses that line the street and to provide a buffer for pedestrians and help calm traffic. On-street parking occupies about half the surface area per car compared to off-street, which requires driveways and aisles for access and maneuvering. Where adequate right-of-way is available and off-street space limited, angled parking can provide additional parking capacity. In such cases, reverse-in angle (or front-out) parking can be considered as an alternative to front-in angled parking. Motorists pulling out of reverse-in angled parking can better see the active street they are entering. This is especially important to bicyclists. Moreover, people exiting cars do so on the curb side and aren t as likely to step into an active travel lane. Bicycle Facility. Bicycle facilities within the traveled way may include bicycle lanes, bicycle boulevards, other types of shared roadways (with or without shared lane markings), and cycle tracks. Although the Leland Bicycle Plan should be consulted to determine whether specific treatments are identified for a given street segment, bicycle lanes are indicated on some street typology cross-sections, and shown as options on others. Designers should carefully consider context in selecting the appropriate treatment. The minimum bicycle lane width is 5 feet, however, since gutter pans should not be included as part of a bike lane, a distance of 7 feet from curb face to lane marking is used in such cases. Refer to the Manual on Uniform Traffic Control Devices (MUTCD) and the 13 Street Design Overview

20 Leland Bicycle Plan for additional design details and guidance on pavement markings and signage. Shared travel lanes may be considered when outside lanes are at least 14 feet wide and travel speeds do not exceed 35 mph. Transit Facility. Transit accommodations within the traveled way may include bus bulbs, bus pullouts, and other features. Median. Medians provide access management by concentrating left turn movements into and out of abutting development to physically defined locations where a separate left turn lane or pocket can be provided. A perceived or actual narrowing can also help suppress travel speeds. The reduced number of conflicts and improved spacing of conflict points can decrease vehicle crashes, while the median itself provides pedestrians with a refuge as they cross the road, and offers space for landscaping, lighting, and utilities. These medians are usually raised and curbed. Landscaped medians enhance the street or can help create a gateway entrance into a community. It is important to identify median configurations early in the design process, to allow for efficient access and convenient connectivity. Medians vary in width, depending on available right-of-way, street typology, design vehicle, and function. The benefits of a wider median must be balanced against additional costs, travel speeds, land use context, and ROW impacts, as well as pedestrian concerns related to total crossing distance. Mountable medians and/or strategically located emergency crossovers may be warranted in the interest of efficient public safety access. 14 Street Design Overview

21 5 Standard Cross-Sections The following two sections illustrate street cross-sections for the street types listed previously, accompanied by a summary of design elements and parameters for each. These illustrations are intended to provide a general understanding of the spatial relationships among the various components street s cross-section. These diagrams represent one or more possible travelway and streetscape configurations. Dimensional guidelines and design specifications provide ranges or minimum/maximum values where flexibility is appropriate or desirable to address specific conditions. These drawings are meant to depict a typical design for a given combination of street and area types. They are not engineering drawings or specifications. Some situations, particularly retrofits of existing streets, may require substantial variations from these typical sections. In no case should these cross-sections be used in isolation; specific local context and the full range of design elements discussed in this document must be considered in decision-making, along with other relevant plans, regulations, and guidelines. Notes on cross-section diagrams: 1. Gutter pan width is included in the dimensioned width of parking lanes, and for travel lanes with design speeds of 25 mph or less. Gutter pans are not included in determining bike lane widths, because the seam between asphalt and concrete can be a cycling hazard. The gutter pan is also excluded from travel lane widths when design speeds exceed 25 mph. 15 Standard Cross-Sections

22 5.2 Conventional Subdivision Cross-Sections This section contains cross-section detail sheets for the following Conventional Subdivision (CSD) street types, inlcuding applicable zoning categories: Local Streets Residential Yield Street R-15/R-6/PUD Residential General Street (Parallel Parking or Bike Lanes) R-15/R-6/PUD Residential Swale Street (with/without Bike Lanes) R-20/R-15/RMH Mixed-Use Streets Main Street C2 Two-Lane Avenue (Divided or Undivided) C1/MF/O&I/RMH Major Streets Four-Lane Avenue, (Parallel Parking or Divided) C1/MF/O&I/RMH Multi-way Boulevard (Angled or Parallel Parking) C2 Industrial, Service, and Access Facilities Industrial Street C3 Residential Alley All residential zones 31 Standard Cross-Sections

23 CSD Residential Yield Street (R-15/R-6/PUD) Residential Yield Streets are low-speed, low-volume, pedestrian-oriented two-way streets providing access and connectivity within neighborhoods. At low speeds, unmarked lanes accommodating parallel parking on only one side allow drivers the time and space to negotiate potential conflicts with oncoming traffic. Residential Yield Streets typically extend less than 1/2 mile, and serve fewer than 40 dwelling units. Both sides of the street include sidewalks, and streetscape amenities are installed at a pedestrian scale. While these streets can be important connectors in the overall bicycle network, bicycle lanes are typically not needed due to low speeds and volumes. C D E F F E D C B A R/W R/W Dimensions A Right-of-way 49' min. B Face-of-curb to face-of-curb 27' C Maintenance strip 6' min. D Sidewalk 5' min. E Planting area 6' min. F Parallel parking/travel lane 13.5' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Curb radii Lighting Permitted furniture Sidewalk Tree lawn 40' o.c. average Parallel (informal, one side only) 25 mph Passenger vehicle 300' As needed No 5-10' Required on all public streets for new development, pedestrian scale optional and responsibility of developer As needed 32 Standard Cross-Sections

24 CSD Residential General Street with Parallel Parking (R-15/R-6/PUD) Residential General Streets are probably the most common and versatile streets in suburban developments, often serving as minor collectors within a neighborhood. They are typically unmarked, and may include on-street parking. Residential General Streets can also be used in residential-compatible mixed-use contexts. Two general travel lanes serve automobiles and some local transit or freight vehicles at moderate-to-low speeds. Sidewalks are required on both sides of the street. Dimensions C D E F G G F E D C B A R/W R/W A Right-of-way 58 62' min. B Face-of-curb to face-of-curb 36 40' C Maintenance strip 6' min. D Sidewalk 5' min. E Planting area 6' min. F Parking 8' G Travel lane 10 12' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Curb radii Lighting Permitted furniture Sidewalk Tree lawn 40' o.c. average Parallel 30 mph DL ' As needed No 5-10' Required on all public streets for new development, pedestrian scale optional and responsibility of developer Bicycle racks, benches, parking meters 33 Standard Cross-Sections

25 CSD Residential General Street with Bike Lanes (R-15/R-6/PUD) Residential General Streets are probably the most common and versatile streets in suburban developments, often serving as minor collectors within a neighborhood. They are typically unmarked, and may include bicycle lanes if warranted by traffic speeds and volumes or for bicycle network continuity. Residential General Streets can also be used in residential-compatible mixed-use contexts. Two general travel lanes serve automobiles, bicycles, and some local transit or freight vehicles at moderate-to-low speeds. Sidewalks are required on both sides of the street. Dimensions C D E F G G F E D C B A R/W R/W A Right-of-way 56 60' min. B Face-of-curb to face-of-curb 34 38' C Maintenance strip 6' min. D Sidewalk 5' min. E Planting area 6' min. F Bike lane 7'* G Travel lane 10 12' *5' paved + 2' gutter pan Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Curb radii Lighting Permitted furniture Sidewalk Tree lawn 40' o.c. average None 30 mph DL ' As needed No 5-10' Required on all public streets for new development, pedestrian scale optional and responsibility of developer Bicycle racks, benches, parking meters 34 Standard Cross-Sections

26 CSD Residential Swale Street (R-20/R-15/RMH) Residential Swale Streets are specialized variations of a common and versatile suburban street type. In certain sensitive environments or under other special conditions, a swale treatment providing open drainage may be more appropriate than curb-and-gutter. This design requires a relatively wide right-of-way, and should be used sparingly in new developments. On-street parking is not compatible with this design. Sidewalks are present on both sides, behind the drainage swales. Dimensions C D E F G H H G F E D C B A R/W R/W A Right-of-way 66 70' min. B Pavement width 20 24' C Maintenance strip 6' min. D Walkway 5' min. E Planting area 6' min. F Drainage area (swale) 10' min. G Grassed shoulder 2' min, H Travel lane 10 12' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Curb radii Lighting Permitted furniture Sidewalk Tree lawn 40 o.c. average None 30 mph Passenger vehicle 300' As needed No 5'-10' Required on all public streets for new development, pedestrian scale optional and responsibility of developer As needed 35 Standard Cross-Sections

27 CSD Residential Swale Street with Bike Lanes (R-20/R-15/RMH) Residential Swale Streets with Bike Lanes are specialized variations of a common and versatile type of suburban street. In certain sensitive environments or under other special conditions, a swale treatment providing open drainage may be more appropriate than curb-and-gutter. This design requires a relatively wide right-of-way, and should be used sparingly in new developments. On-street parking is not compatible with this design. When necessary for network continuity, or if roadway alignment or traffic speeds and volumes make a shared travel lane undesirable, a bike lane may be appropriate. Sidewalks are present on both sides, behind the drainage swales. Dimensions C D E F G H I I H G F E D B A R/W A Right-of-way 76 80' min. B Pavement width 30 34' C Maintenance strip 6' min. D Walkway 5' min. E Planting area 6' min. F Drainage area (swale) 10' min. G Grassed shoulder 2' min. H Bike lane 5' I Travel lane 10 12' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Curb radii Lighting Permitted furniture Sidewalk Tree lawn 40 o.c. average None 30 mph Passenger vehicle 300' As needed No 5'-10' Required on all public streets for new development, pedestrian scale optional and responsibility of developer As needed C R/W 36 Standard Cross-Sections

28 CSD Main Street (C2) Main Streets can function as low-speed arterials, collectors, or even local streets, depending on location and context. They can connection neighborhoods an and districts, as well as providing access between local and higher-level streets. Often acting as the primary destination street serving a mixed-use center of social or commercial activity, Main Streets are highly walkable. Emphasis on pedestrian travel requires wide sidewalks, crosswalks, and pedestrian amenities. On-street parking is typically provided on both sides of the street, and bicycle lanes are typically not warranted due to lower speeds and volumes, and the desire to minimize pedestrian crossing distances. R/W C D E F F E D C B A R/W Dimensions A Right-of-way 79 83' min. B Front-of-curb to front-of-curb 37 41' C Sidewalk 15' min. D Furniture zone 6' min. E Parking lane 8.5' F Travel lane 10 12' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Sidewalk Tree grate 40' o.c. average Parallel 25 mph WB ' >100' apart No Curb radii 10' Lighting Permitted furniture Required on all public streets for new development, pedestrian scale optional and responsibility of developer Bicycle racks, benches, parking meters, shelters 37 Standard Cross-Sections

29 CSD Two-Lane Avenue, Undivided (C1/MF/O&I/RMH) These Avenues are low-speed streets providing access to abutting commercial and mixed uses, including larger internally-oriented subdivisions and detached development with large setbacks. They serve as primary bicycle and pedestrian routes, and may accommodate local transit vehicles. Two-Lane Avenues have sidewalks on both sides, and typically include bike lanes. They may or may not include a median but do not provide on-street parking. C D E F G G F E D C B A R/W R/W Dimensions A Right-of-way 58 62' min. B Face-of-curb to face-of-curb 34 38' C Maintenance strip 8' min. D Sidewalk 6' min. E Planting area 6' min. F Bike lane 7'* G Travel lane 10 12' * 5 bike lane, 2 gutter pan Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Sidewalk Tree lawn 40' o.c. average None 30 mph WB ' 100' No Curb radii 15' Lighting Permitted furniture Required on all public streets for new development, pedestrian scale optional and responsibility of developer Bicycle racks, benches, parking meters, shelters 38 Standard Cross-Sections

30 CSD Two-Lane Avenue, Divided (C1/MF/O&I/RMH) These Avenues are low-speed streets providing access to abutting commercial and mixed uses, including larger internally-oriented subdivisions and detached development with large setbacks. They serve as primary bicycle and pedestrian routes, and may accommodate local transit vehicles. Two-Lane Avenues have sidewalks on both sides, and typically include bike lanes. They may or may not include a median but do not provide on-street parking. C D E F G H G F E D C B A R/W R/W Dimensions A B Right-of-way with center turn lane with median Face-of-curb to face-of-curb with center turn lane with median 70 74' min. 75' min ' min ' min. 48' 52 56' C Maintenance strip 2' min. D Sidewalk 6' min. E Planting area 6' min. F Bike lane 7.5' G Travel lane 10 12' H Center lane striped turn lane median 11' 17' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Median opening distance Partial medians/island Sidewalk Tree lawn 40' o.c. average None 35 mph WB ' 100' >200' apart No Curb radii 15' Lighting Permitted furniture Required on all public streets for new development, pedestrian scale optional and responsibility of developer Bicycle racks, benches, parking meters, shelters 39 Standard Cross-Sections

31 CSD Four-Lane Avenue, Parallel Parking (C1/MF/O&I/RMH) These Avenues may function as either arterials or major collectors, but are typically urban in character, balancing moderate-speed, pedestrian-friendly access and mobility to residential or mixed-use development. They can serve a range of traffic volumes within or between various area types. On-street parking provides access to adjacent development as well as buffering pedestrians from traffic. Sidewalks and bicycle lanes are present on both sides. C D E F G G H G G F E D C B A R/W R/W Dimensions A Right-of-way ' min. B Face-of-curb to face-of-curb 70 91' C Sidewalk 15' D Planting area 6' min. E Parallel parking lane 8' F Bike lane 5' G Travel lane 10 12' H Median 4 17' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Median opening distance Partial medians/island Sidewalk Tree grate/lawn 40' o.c. average Parallel 40 mph WB ' 200' 200' min. (may be increased to accommodate a turn lane providing necessary storage length & appropriate taper) Yes Curb radii 15' Lighting Permitted furniture Required on all public streets for new development, pedestrian scale optional and responsibility of developer Bicycle racks, benches, parking meters, shelters 40 Standard Cross-Sections

32 CSD Four-Lane Avenue, Divided (C1/MF/O&I/RMH) These Avenues function as arterials, providing mobility to larger volumes of through traffic, and are not suitable for on-street parking. However, bike lanes and buffered sidewalks are present on both sides of the street. Medians provide refuges for crossing pedestrians. C D E F G G H G G F E D C B A R/W R/W Dimensions A Right-of-way ' min. B Face-of-curb to face-of-curb 58 79' C Maintenance strip 10' min. D Sidewalk 6' min. E Planting area 6' min. F Bike lane 7' * G Travel lane 10 12' H Median 4 17' * 5 bike lane, 2 gutter pan Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Median opening distance Partial medians/island Sidewalk Tree grate/lawn 40' o.c. average None 40 mph WB ' 200' Only at intersections Yes Curb radii 20' Lighting Permitted furniture Required on all public streets for new development, pedestrian scale optional and responsibility of developer Benches, shelters 41 Standard Cross-Sections

33 CSD Multi-way Boulevard, Parallel Parking (C2) This cross-section applies to main entrances of high-volume malls, corporate offices, strip shopping centers, and other major developments. Pedestrian and vehicular access is provided, with sidewalks along both sides of the curb-and-gutter street. Although such access drives are typically on private easements, these guidelines are designed to facilitate conversation to public use as part of a future conversion to a grid-based infill redevelopment. C D E F G H H I H H G F E D C R/W B 1 B 2 B 2 A R/W Dimensions A Right-of-way ' min. B 1 Face-of-curb to face-of-curb 65 73' min. B 2 Face-of-curb to face-of-curb 18 20' C Sidewalk 10' D Planting area 10' E Parking lane 8' F Access lane 10 12'* G Median 11' H Travel lane 12 14'* I Median 17' min. *Includes 2 gutter pans Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Median opening distance Partial medians/island Curb radii Lighting Permitted furniture Bicycle treatment Sidewalk Tree grate/lawn 40 o.c. average Parallel in slip lane mph in general lanes WB-40, BU-40 (general lanes); DL-23 (slip lanes) 600' 200' Only at intersections Yes 15 20' Required on all public streets for new development, pedestrian scale optional and responsibility of developer Benches, shelters Shared in slip lanes for designated bus/truck routes 42 Standard Cross-Sections

34 CSD Multi-way Boulevard, Angled Parking (C2) This cross-section applies to main entrances of high-volume malls, corporate offices, strip shopping centers, and other major developments. Pedestrian and vehicular access is provided, with sidewalks along both sides of the curb-and-gutter street. Although such access drives are typically on private easements, these guidelines are designed to facilitate conversation to public use as part of a future conversion to a grid-based infill redevelopment. C D E F G H H I H H G F E D C R/W B 1 B 2 B 2 A R/W Dimensions A Right-of-way ' min. B 1 Face-of-curb to face-of-curb 65 73' min. B 2 Face-of-curb to face-of-curb C Sidewalk 10' D Planting area 10' E Parking lane 8' 29 31' 27 29' 25 27' F Access lane 10 12'* G Median 11' H Travel lane 12 14'* I Median 17' min. *Includes 2 gutter pans Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Median opening distance Partial medians/island Curb radii Lighting Permitted furniture Bicycle treatment Sidewalk Tree grate/lawn 40 o.c. average Angled in slip lane mph in general lanes WB-40, BU-40 (general lanes); DL-23 (slip lanes) 600' 200' Only at intersections Yes 15 20' Required on all public streets for new development, pedestrian scale optional and responsibility of developer Benches, shelters Shared in slip lanes for designated bus/truck routes 43 Standard Cross-Sections

35 CSD Industrial Street (C3) Areas of significant industrial development, along with some service and commercial districts, carry higher volumes of large trucks, even if total traffic volumes tend to be lower. In addition to thicker pavement, accommodating larger vehicles requires wider lanes and larger turn radii. Generous parallel parking lanes are provided for wider vehicles, but slow speeds and low parking and traffic volumes eliminate the need for bicycle lanes. Industrial streets have curbs-and-gutters and sidewalks on both sides. C D E F G G F E D C B A R/W R/W Dimensions A Right-of-way 72 74' min. B Face-of-curb to face-of-curb 40 42' C Maintenance strip 8' min. D Sidewalk 10' min. E Planting area 6' min. F Parallel parking lane 8 9' G Travel lane 12' Standards Walkway type Planting type Tree spacing Parking type Design speed Design vehicle Minimum desirable intersection spacing Minimum desirable driveway spacing Partial medians/island Curb radii Lighting Permitted furniture Sidewalk Tree lawn 40' o.c. average Parallel 35 mph WB ' As needed No 25'+ Required on all public streets for new development, pedestrian scale optional and responsibility of developer As needed 44 Standard Cross-Sections

36 CSD Residential Alley (All Residential Zones) Residential alleys can provide low-speed access to rear-entry parking and for accessory units. They can also serve as a location for utilities and sanitation services. Alleys can also be safe, efficient shortcuts for pedestrians and cyclists, and can readily incorporate permeable pavements and other low-impact materials and techniques. Sanitation trucks and emergency vehicles must be able to easily navigate alleys and their turn radii. B A Dimensions A Easement width 20' min. B Travel lane 16' min. B Travel lane, fire service route 20' 45 Standard Cross-Sections

37 6 Planning and Design Guidelines 6.1 Design Vehicles The selected design vehicle (sometimes referred to as control vehicle ) influences several geometric design features including lane width, corner radii, median nose design, and other intersection design details. Designing for a larger vehicle than necessary is undesirable, due to potential negative impacts larger dimensions may have on pedestrian crossing distances and the speed of turning vehicles. Designing for a vehicle that is too small can result in operational and safety problems if larger vehicles frequently use the facility. For design purposes, the WB-40 (wheel-base 40 feet) is adequate unless larger vehicles are more common. On bus routes and truck routes, designing for the bus (CITY-BUS or similar) or large truck (either the WB-50 or WB-62/WB-67 for 53-foot long trailers) may be appropriate, but primarily at intersections where these vehicles make turns. For example, for intersection geometry design features such as corner radii, different design vehicles should be used for each intersection or even each corner, rather than a one-size-fits-all approach, which results in larger radii than needed at most corners. Ideally, the design vehicle should be accommodated without encroachment into opposing traffic lanes; however, it is generally acceptable to allow infrequent encroachment of short duration onto multiple same-direction traffic lanes on the receiving roadway. In cases where a larger vehicle uses a 2-lane road only infrequently, it may be appropriate to allow encroachment into the opposing traffic lane, especially if traffic volumes and speeds are relatively low. The costs and impacts of designing for such a rare event may be excessive. In some cases, travel by larger vehicles may be prohibited, or limited to off-peak hours. 46 Planning and Design Guidelines

38 The design vehicle(s) selected for each of the street types included in these Guidelines are listed on the corresponding cross-section sheets. Design vehicles used include: P Passenger Car DL-23 Delivery Van SU-30/SU-40 Single Unit Truck BU-40 Large School Bus WB-40/WB-50 Intermediate Semitrailer WB-62/WB-67 Interstate Semitrailer The following references provide more details on design vehicles: A Policy on Geometric Design of Highways and Streets, 6th Edition, NACTO Urban Street Design Guide, All streets shall appropriately accommodate emergency vehicles. 6.2 Design Speed The application of design speed for complete streets can differ philosophically from conventional transportation practices. Traditionally, the approach for setting design speed is to use as high a design speed as practical. This approach can have negative effects, especially in more urbanized areas. High design speeds may discourage pedestrian travel and access, and can impact the social and retail life of a street and its adjacent land use. Local economies benefit from pedestrian activity. In contrast to this approach, the goal for complete streets is to establish a design speed that reflects the function of the street and which is appropriate for the surrounding context. This creates a safer and more comfortable environment for motorists, pedestrians, and bicyclists. This approach also enhances access to adjacent land, potentially increasing its value. For complete streets in a more urban/suburban setting, design speeds of 20 to 35 mph are desirable. Alleys and narrow roadways intended to function as shared spaces may have design speeds as low as 10 mph. Design speed does not determine nor predict at what exact speed motorists will travel on a roadway segment; rather, design speed determines which design features are allowable (or mandated). Features associated with high-speed designs, such as large curb radii, straight and wide travel lanes, ample clear zones (no on-street parking or street trees), guardrails, etc., may degrade the walking experience and make it difficult to create complete streets. The design of the road and its function can encourage higher travel speeds. A slower design speed allows the use of features that enhance the walking environment, such as smaller curb radii, narrower sections, trees, on-street parking, curb extensions, and street furniture, which in turn can help moderate traffic speeds and encourage pedestrian travel. 47 Planning and Design Guidelines

39 Design speeds higher than 35 mph should not normally be used within residential neighborhoods or downtown commercial districts, or in Transects T-3 or higher, with the exception of some major facilities. The design speeds recommended for each of the street types included in these Guidelines are listed on the corresponding cross-section sheets. 6.3 Access Management A major challenge in street design is balancing the number and locations of street access points. There are many benefits of well-connected street networks. The majority of conflicts between users occur at intersections and driveways. The presence of closely-spaced driveways in addition to the necessary intersections creates many conflicts between vehicles entering or leaving a street and bicyclists and pedestrians riding or walking along the street. Before After Figure 2. Adding medians and consolidating driveways to manage access. (Credit: Michele Weisbart) Access management through managing driveways and providing strategically located raised medians has many benefits: The number of conflict points is reduced, especially by replacing center two way left turn lanes with raised medians since left turns by motorists account for a high number of crashes with bicyclists and pedestrians. Pedestrian crossing opportunities are enhanced with a raised (refuge) median. 48 Planning and Design Guidelines

40 Universal access for pedestrians is easier, since the sidewalk is less frequently interrupted by driveway slopes. Fewer driveways result in more space available for higher and better uses. Improved traffic flow and quality of service may reduce the need for road widening, allowing part of the right-of-way to be recaptured or retained for other users. Figure 3. Corner with many wide driveways (left) and reconstructed corner with fewer, narrower driveways (right). (Credit: Michele Weisbart) The following possible negative effects of management should be considered and addressed: Providing access management along a street can improve mobility and may reduce delays and increase motor vehicle speeds and volumes, which can impact other users. Modified access to businesses may require in direct connections and alternate routes of ingress and egress for all users, including walkers and bicyclists. Concrete barriers and overly-landscaped medians may act as barriers to pedestrian crossings. Medians should be designed with no more than normal curb height and with landscaping that allows pedestrians to see to the other side. Adjacent land uses can experience less direct access. Careful planning of access management considers this. One way to achieve effective access management while minimizing the potential drawbacks described above is through the use of backage roads. These facilities function like frontage roads, but are located at the rear of properties, allowing buildings to front more directly on the street they are facing. Such configurations can improve traffic flow by better maintaining adequate intersection spacing, and may offer better options for bicycle routing. They can also encourage a more cohesive and attractive street corridor, providing better opportunities for streetscape amenities, and more supportive conditions for transit and pedestrians. Appropriate interconnectivity between parcels can also improve accessibility, as well as enabling shared parking, thereby reducing impervious surface area. 49 Planning and Design Guidelines

41 6.3.1 Offset Driveways Negative offset driveways exist when an approaching vehicle encounters a driveway on the right-hand side of the road, followed by a driveway on the left (see Figure 4). Negative offsets should be avoided, especially in the presence of a center two-way left-turn lane (TWLTL). Such circumstances greatly increase chances of a serious head-on collision between two oncoming vehicles making simultaneous left turns from the TWLTL. The positive offset depicted in Figure 4 minimizes conflicts, reducing crash potential. If a positive driveway offset is not feasible, direct alignment is the next best option. Figure 4. Driveway offsets. (Source: Access Management in the Vicinity of Intersections Technical Summary, FHWA-SA ) Driveway and Intersection Spacing The issue of driveway spacing is fundamental to access management. The Policy on Street and Driveway Access to North Carolina Highways states the following: Where more than one driveway is permitted along a single property frontage, the distance, D, measured along the right-of-way line between the tangent projection of the inside edges of adjacent driveways shall be at least 100 feet. For high volume traffic generators, the minimum distance between the centerlines of fullmovement driveways into developments that generate high traffic volumes should be at least 600 feet for most non-critical transportation corridors and a minimum of 1,000 feet for Major Thoroughfares, National Highway System and Intrastate Routes, Primary Routes, and Corridors with identified safety concerns. For clearance to intersection corners, the same source cites a desirable minimum of 100 between the points of tangency of the intersection radius curvatures. However, some jurisdictions suggest minimum distances of up to 300 on major streets. 50 Planning and Design Guidelines

42 Intersection spacing is a more complex issue, involving factors beyond access management. The planning of an efficient street network involves spacing roads based on their functional hierarchy (from freeway to arterial to collector to local). However, the somewhat idealized spacings suggested in numerous references are highly sensitive to geographic constraints, as well as variations in the intensity and types of land uses served. There are also competing objectives. In terms of moving large volumes of traffic quickly, the number of intersections should be minimized to reduce conflicts. The long intersection spacings that result, however, are discourage pedestrian and bicycle travel, and result in inefficient transit service. The spacing recommendations in the following tables (one for Flexcode, and one for CSD) attempt to balance these objectives in the context of an urbanizing community striving to promote multi-modal travel. Table 3. Recommended driveway and intersection spacing (Flexcode). Flexcode Thoroughfare Transect Zone Minimum Desirable Driveway Spacing Minimum Desirable Street Spacing Highways T2 As needed 0.5 to 1 mile Roads Streets/Drives Avenues T2 As needed 300 T3 As needed 300 T3/T4 As needed 300 T4O/T5 As needed 150 T3/T T4O/T Multi-Way Boulevards T4O/T Commercial Streets T4O/T Table 4. Recommended driveway and intersection spacing (CSD). CSD Typology Minimum Desirable Driveway Spacing Minimum Desirable Street Spacing All Residential Streets As needed 300 Main Streets As needed 300 Two-Lane Avenues Four-Lane Avenues Multi-Way Boulevards Industrial Streets As needed Planning and Design Guidelines

43 6.4 Designing Streets for Transit Public transit serves a vital transportation function for many people; it is their access to jobs, school, shopping, recreation, visitation, worship, and other daily functions. For transit to provide optimal service, streets must accommodate transit vehicles as well as access to stops. Transit connects passengers to destinations and is an integral component of shaping future growth into a more sustainable form. Transit design should also support placemaking. Public transit should be planned and designed as part of the street system. It should interface seamlessly with other modes, recognizing that successful transit depends on customers getting to the service via walking, bicycling, car, taxi, or paratransit. Transit planning should follow these principles: ½ ½ Transit service should be convenient, frequent, dependable, and cost-effective. Transit stops should be: Easily accessible, with safe and convenient crossing opportunities. Active and attractive public spaces that attract people on a regular basis, at various times of day, and all days of the week. Include amenities for passengers waiting to board. Attractive and visible from a distance. Designed and located to influence accessibility to transit and network operations, as well as travel behavior/mode choice. Transit stops should provide space for a variety of amenities in commercial areas, to serve residents, shoppers, and commuters alike. Zoning codes, local land use ordinances, and design guidelines around transit stations should encourage walking and a mix of land uses. Streets that connect neighborhoods to transit facilities should be especially attractive, comfortable, and safe and inviting for pedestrians and bicyclists Access to Transit Transit depends primarily on walking to function well; most transit users walk to and from transit stops. Sidewalks on streets served by transit and on the streets that lead to transit corridors provide basic access. Bicycle-friendly streets do the same for those who access transit by bicycle. Transit trips should be provided with a safe and convenient street crossing at the transit stop to avoid disproportionally high number of pedestrian crossing crashes in the vicinity of transit stops. Every transit stop should be evaluated for its crossing opportunities. If the crossing is deemed unsafe, mitigation can occur in two ways: a crossing should be provided at the existing stop, or the stop can be moved to a location with a safer crossing. Simply stated, there should not be transit stops without means to safely and conveniently cross the street. 52 Planning and Design Guidelines

44 6.4.2 Bus Stop Design Elements The following sections provide guidance for designing bus stops. A well placed and configured transit stop offers the following characteristics: Clearly defines the stop as a special place. Provides a visual cue on where to wait for a transit vehicle. Does not block the path of travel on the adjacent sidewalk. Allows for ease of access between the sidewalk, the transit stop, and the transit vehicle. Layout guidelines include the following: Consolidate streetscape elements to create a clear waiting space and minimize obstructions between the sidewalk, waiting area, and boarding area. Consider the use of special paving treatments or curb extensions (where there is on-street parking) to distinguish transit stops from the adjacent sidewalks. Integrate transit stops with adjacent activity centers whenever possible to create active and safe places. Avoid locating bus stops adjacent to driveways, curb cuts, and land uses that generate a large number of automobile trips (gas stations, drive-thru restaurants, etc.). Figure 5. ADA compliant bus stop. (Credit: Michele Weisbart) Transit stops are required by the Americans with Disabilities Act (ADA) to be accessible. Specifically, ADA requires a clear loading area (minimum 5 feet by 8 feet) perpendicular to the curb with a maximum 2 percent cross-slope to allow a transit vehicle to extend its lift to allow people with disabilities to board. The loading area should be located where the transit vehicle has its lift and be accessible directly from a transit shelter. The stop must also provide 30 by 40 inches of clear space within a shelter to accommodate wheelchairs. The greater use of lowfloor transit vehicles may make this requirement moot; but it will still be necessary to provide enough room so wheelchair users can access all doors. The essential streetscape elements for transit include signs, shelters, and benches. Benches should be provided at transit stops with headways longer than five minutes. Shelters keep waiting passengers out of the rain and sun and provide increased comfort and security. Shelters vary in size and design; standard shelters are 3 to 7 feet wide and 6 to 16 feet long. They include covered seating and sign panels that can be used for transit information. Shelters should: 53 Planning and Design Guidelines

45 Be provided at transit stops with longer headways. Have electrical connections to power lighting and/or real-time transit information, or accommodate solar power. Be set back from the front of the bus stop to allow the bus to merge into travel lanes when the stop is located at the far side of an intersection or at a mid-block location. This setback is not required when the stop is located at the near side of the intersection or at a bus bulb. Shelters should be located so they don t conflict with the pedestrian zone. Shelters should not block building entrances or the pedestrian zone. Transit stops should also provide other amenities to make waiting for the next bus comfortable. Trash/recycling receptacles should be provided and maintained at most stops Bus Stop Placement Optimal placement of a bus stop depends on characteristics of both the roadway and the transit system. At signalized intersections, far-side placement of bus stops is generally preferred, while near-side stops are typically better suited to stop sign-controlled intersections. Each placement (as well as mid-block locations) has its advantages and disadvantages, summarized in Table 5. In any case, the location offering the safest, most convenient passenger service should be preferred. 54 Planning and Design Guidelines

46 Table 5. Bus stop placement considerations. Location Advantages Disadvantages Near Side Far Side Mid-block Minimizes interference when traffic is heavy on the far side of an intersection. Provides an area for a bus to pull away from the curb and merge with traffic. Minimizes the number of stops for buses. Allows passengers to board and alight while the bus is stopped at a red light. Allows passengers to board and alight without crossing the street if their destination is on the same side of the street. Most important where one side of the street has an important destination, such as a school or employment center that generates more passenger demand than the far side. Minimizes conflicts between right-turning vehicles and buses. Optimal location for traffic signal synchronized corridors. Provides additional right-turn capacity by allowing traffic to use the right lane. Improves sight distance for buses approaching intersections. Requires shorter bus deceleration distances. Signalized intersections create traffic gaps for buses to reenter traffic lanes. Improves pedestrian safety as passengers cross in back of the bus. Minimizes sight distance problems for pedestrians and vehicles. Boarding areas experience less congestion and conflicts with pedestrian travel paths. Can be located adjacent to or directly across from a major transit midblock use generator. Increases conflicts with right-turning vehicles. Stopped buses may obscure curb-side traffic control devices and crossing pedestrians. Obscures sight distances for vehicles stopped to the right of the buses. Decreases roadway capacity during peak periods due to buses queuing in through lanes near bus stops. Decreases sight distance of on-coming traffic for pedestrians crossing intersections. Can delay buses arriving in the green signal phase but finishing during the red phase. Less safe for passengers crossing in front of the bus. Queuing buses may block the intersection during peak periods. Sight distance may be obstructed for vehicles approaching intersections. May increase the number of rear-end accidents if drivers do not expect a bus to stop after crossing an intersection. Stopping both at a signalized intersection and a far-side stop may interfere with bus operations. Decreases on-street parking supply (unless mitigated with a curb extension). Requires a mid-block pedestrian crossing. Increases walking distance to intersections. Stopping buses and mid-block pedestrian crossings may disrupt mid-block traffic flow. (Source: Federal Transit Administration, BRT Stops, Spacing, Location, and Design, 55 Planning and Design Guidelines

47 6.4.4 Bus Pull-Outs versus In-Lane Stops Curbside pull-out stops can be an efficient, low-cost option for bus stops on streets with curbside parking. The bus stop replaces on-street parking, requiring only signage/pavement marking and ADA-compliant boarding. These types of stops prioritize through-traffic, so are most appropriate are most maintaining flow is a priority, or where in-lane stops are not desirable, such as layover stops. Curbside pull-outs are appropriate when bus frequency is relatively low land speeds exceed 35 mph. Some on-street parking will be lost, and extra time is required for bus transitions, especially when re-entering traffic. Additional considerations to be addressed include bus-bicycle conflicts, and adequacy of sidewalk width. Finally, the bus stop zone must be wide enough to ensure buses do not extend into adjacent lanes. Pull-out bays that extend beyond the normal curbline and into the sidewalk should usually be avoided unless sidewalks are very wide or can be shifted. Such pull-outs involve considerably more expense, and need to be long. They can create delays when buses exit and then attempt to re-enter traffic. Even with adequate entry and exit tapers, buses may not consistently park close enough to the curb to ensure easy boarding and alighting. In-lane stops are a very common bus stop solution, due to low cost and ease of implementation. Only signage and an ADA-compliant boarding area are needed at a safe and convenient location, along an existing curbside served by sidewalks. In-lane stops are best suited to mixed-traffic streets posted at 30 mph or less, where bus service is not highfrequency. By eliminating shifts in-and-out of traffic lanes, in-lane stops save wear on buses and reduce bus delays. Stop zones should be at least as long as the bus, and both front and back passenger doors should be accommodated. Care must be taken in dealing with separate bike lanes or shared travel lanes, such as shifting to the left of the bus in advance of the stop. Passengers typically alight directly from the sidewalk or suitable pad. Especially on busy two-lane, two-way streets, in-lane stops can impede following traffic. At hazardous locations, it may be necessary to discourage passing of buses. Occasional pull-out stops can be provided to allow vehicles to pass stopped buses. Regardless of the type of bus stop, the stop zone must provide at least feet of clearance from crosswalks to provide clear sight distances for pedestrians, cyclists, and drivers. Bus stop amenities should not block the accessible boarding area or pedestrian routes. Adequate space should also be provided to minimize conflicts with general pedestrian flows. Mid-block stops should be used only in special circumstances, where stops at intersections create safety concerns or are too far and inconvenient. Pedestrian crossings at mid-block stops should have signalized or traffic-calmed treatments, and must be well-lighted. 56 Planning and Design Guidelines

48 6.4.5 Example Bus Stop Guidance Specific decisions about bus stop placement and design depend heavily on funding; anticipated passenger demand; locational context, right-of-way availability and ownership; engineering judgment; zoning; and other legal or regulatory agreements. The transit agency servicing this region, the Cape Fear Public Transportation Authority (known as WAVE Transit), has developed guidelines for bus stop location. Key elements are summarized below: Bus Stop Amenities. A three-tier hierarchy based primarily on weekday boardings to determine bus stop amenities. Figure 6. Hierarchy of bus stop amenities. (Source: Cape Fear Public Transit Authority) Zoning. City of Wilmington land use ordinances provide density bonuses for bus stop or shelter provision in mixed-use and residential planned unit developments. Right-of-Way. WAVE Transit must obtain a voluntary user agreement with private property owners, detailing the space to be set aside and possible amenities. In NCDOT ROW, the standard Bus Shelter Encroachment Process is followed. Comprehensive Planning. The City of Wilmington s 2013 Comprehensive Plan sets the direction and nature of growth for a 25-year period. The plan s details policies that promote the location and design of bus stops. These policies include: New developments within existing and planned transit corridors should provide transit easements for bus stops. Bus shelters, seating, and related elements should be provided at stop locations, where appropriate. 57 Planning and Design Guidelines

49 The dedication of land for construction of transit stations and stops within mixed use centers should be part of the development review process. Engineering Judgement and Design Criteria. The site design process for bus stop and or bus shelter is specific to each individual project. ADA requirements serve as a design floor, and additional design elements may be identified and required by the project s sponsors. The NCDOT maintains its own set of design criteria, and these items include: Posted speed limit of the adjacent roadway should be 45 mph or less for bus shelter and bus bench installations. In standard 2-6 curb and gutter installations, the bus shelter should be located behind the sidewalk. The minimum distance from the edge of pavement (edge of gutter) to the face of the bus shelter structure or bus shelter bench is: 12 ft. for 45 mph; 10 ft. for 35 mph; and 8 ft. for 25 mph. In shoulder section and mountable curb installations, the bus shelter or bus bench should be located outside the clear recovery area as defined by the latest version of the AASHTO Roadside Design Guide. The Bus Shelter Manufacturer/Vendor must have a North Carolina Licensed Professional Engineer (PE), seal, sign and date the NCDOT Product Evaluation Program Bus Shelter Structural Adequacy Document. (Source: WAVE Transit) 6.5 Other Geometric Design Elements Vertical Alignment The American Association of State Highway and Transportation Officials (AASHTO) Geometric Design of Highways and Streets manual (AASHTO Green Book) provides values for designing vertical curves for living streets. The values used in design of vertical curve design should be selected based on the design speed appropriate for the context of the street. Using higher values can influence vehicle speeds and may require greater impacts to the natural terrain and environment Horizontal Alignment The AASHTO Green Book provides values for designing horizontal curves for living streets. The values used in horizontal curve design should be selected based on the design speed appropriate for the context of the street. Using higher values can increase vehicle speeds as well as affecting the character of the street. Larger horizontal curves may also create a more suburban or rural highway feel Sight Distance STOPPING SIGHT DISTANCE The AASHTO Green Book provides appropriate values for designing stopping sight distance for living streets. The 2004 AASHTO Guide for Achieving Flexibility in Highway Design is based on research concerning the establishment of stopping sight distance. The document states 58 Planning and Design Guidelines

50 that the established values for stopping sight distance are conservative and provide adequate flexibility without creating increased crash risk. Consequently, appropriate design speed selection is critical to avoid overly negative impacts to features such as on-street parking and tree planting. INTERSECTION SIGHT DISTANCE Intersection sight distance should be calculated in accordance with the AASHTO Green Book using the design speed appropriate for the street being evaluated. When executing a crossing or turning maneuver onto a street after stopping at a stop sign, stop bar, or crosswalk, drivers will move slowly forward to obtain sight distance (without intruding into the crossing travel lane) stopping a second time as necessary. Therefore, when curb extensions are used or onstreet parking is in place, the vehicle can be assumed to move forward on the second step movement, stopping just shy of the travel lane, increasing the driver s potential to see further than when stopped at the stop bar Horizontal Clearance/Clear Zone Horizontal clearance is the lateral distance from a specified point on the roadway, such as the edge of the travel lane or face of the curb, to a roadside feature or object. The clear zone is the relatively flat unobstructed area that is to be provided for safe use by errant vehicles and vehicles making evasive maneuvers. In urban areas, horizontal clearance based on clear zone requirements for rural and suburban highways is not practical because urban areas are characterized by more bicyclists and pedestrians, lower speeds, more dense abutting development, closer spaced intersections and accesses to property, higher traffic volumes, and restricted right-of-way. Therefore, streets with curbs and gutters in urban areas do not have sufficiently wide roadsides to provide clear zones. Consequently, while there are specific horizontal clearance requirements for these streets, they are based on clearances for normal operation and not based on maintaining a clear roadside for errant vehicles. A suggested minimum horizontal clearance is 1.5 feet measured from the face of the curb. This is primarily intended for sign posts and poles, so they aren t hit by large vehicles with overhangs maneuvering close to the curb Traveled Way Lighting Pedestrians are at a greater risk of being hit when visibility is poor: at dusk, night, and dawn. Many crossings are not lit. Providing improved delineation, conspicuity, illumination or improving existing lighting can improve nighttime safety at intersections and midblock crossings, as motorists can better see and react to pedestrians. Pedestrian scale lighting along sidewalks provides greater comfort and security, especially for people walking alone at night. Transit stops require both kinds of lighting: illumination of the traveled way for safer street crossing, and pedestrian scale illumination at the stop or shelter for security. FHWA-HRT , Informational Report on Lighting Design for Midblock Crosswalks, (April 2008) is a very good resource. It also contains very useful information about lighting design for pedestrians at intersections. 59 Planning and Design Guidelines

51 If bus stops are present between roadway sections, it is necessary to illuminate the roadway and the bus stop. The lighting at the bus stop is essential to provide safety for transit users. Bus stops have high pedestrian activity; therefore, it is necessary to provide adequate lighting at these facilities Designing to Moderate Traffic Speeds To address perceived speeding problems, communities often request the addition of trafficcalming treatments to existing streets. The study and implementation of such strategies is a topic for a separate guidance document. However, certain design elements can be incorporated into original plans to help suppress or moderate speeds to varying degrees. Lane width. Narrower lanes encourage drivers to be more cautious of oncoming traffic. On-street parking. Parked cars narrow the street, creating a perception of friction that slows traffic. Horizontal alignment. Introducing subtle curves can control sightlines, reducing the tendency to increase speed on long straightaways. Street trees. Appropriately placed trees narrow the driver s field of vision without obstructing it, and create a rhythm that can help reduce speed. Building frontages. A built environment with minimal setbacks limits sightlines and increases alertness in the driver. 60 Planning and Design Guidelines

52 7 Intersection Design Most conflicts between roadway users occur at intersections and driveways, where travelers cross each other s path. Good intersection design indicates to those approaching the intersection what they must do and who yields. Conflicts for pedestrians and bicyclists are exacerbated due to their greater vulnerability, lesser size, and reduced visibility to other users. This section describes design considerations in intersection and roundabout geometry, plus other features to improve safety, accessibility, and mobility for all users. 7.1 Principles of Intersection Design The following principles apply to all users of intersections: Good intersection designs are compact. Unusual conflicts should be avoided. Simple right-angle intersections are generally best for all users since intersection problems can be worse at skewed and multi-legged, complex intersections. Free-flowing movements should be avoided. Access management practices should be used to reduce vehicular conflict points near the intersection. Vegetation and other temporary or permanent signs, decorations, electrical housings, or other furnishings should not obstruct sight triangles for pedestrians, bicyclists, or motorists. Intersections involving multi-lane streets introduce additional risks for pedestrians, in particular, due to the introduction of multi-threat scenarios. 61 Intersection Design

53 Careful attention must be paid to mixing zones where motor vehicles and bicycles cross lanes or transition to a different facility type or cross-section. Weaving and merging movements are especially hazardous. 7.2 Intersection Geometry Intersection location and geometry is a critical element of intersection design, regardless of the type of traffic control used. Geometry sets the basis for how all users traverse intersections and interact with each other. The principles of intersection geometry apply to both street and driveway intersections and freeway on- and off-ramps Intersection Skew Skewed intersections occur when roads connect at other than a 90-degree angle. They are generally undesirable, and introduce the following complications for all users: The travel distance across the intersection is greater, which increases exposure to conflicts and lengthens signal phases for pedestrians and vehicles. Skews require users to crane their necks to see other approaching users, making it less likely that some users and regulatory devices will be seen. Obtuse angles may encourage speeding or rolling stops. To mitigate the problems with skewed intersections, several options are available: Reasonable efforts should be made to design or redesign the intersection closer to a right angle physically or through improved channelization and delineation. Some rightof-way may be needed for physical realignments, but this can be offset by the larger area no longer needed for the intersection, which can be sold back to adjoining property owners or repurposed for other uses such as a pocket park, rain garden, greenery, etc. Pedestrian refuges should be considered if the crossing distance exceeds approximately 40 feet. General use travel lanes and bike lanes may be striped with dashes to guide bicyclists and motorists through a long undefined area. Figure 7. Realigning a skewed intersection (left) to a right-angle connection (right) results in less exposure distance and better visibility for all users. (Credit: Michele Weisbart) 62 Intersection Design

54 Multi-leg intersections (more than two approaching roadways) are generally undesirable and introduce the following complications for all users: Multiple conflict points are added as users arrive from several directions. Users may have difficulty assessing and navigating all approaches to identify all possible conflicts and turning options, and in determining who has the right-of-way. At least one leg will be skewed. Users must cross more lanes of traffic and the total travel distance across the intersection is increased. Traffic control of non-traditional five leg type intersections can be problematic. To alleviate the problems and limitations of complex multi-leg intersections, several options are available: Efforts should be made to reduce the number of approaches. This is accomplished by removing one or more legs from the major intersection and creating a minor intersection further up or downstream. As an alternative, one or more of the approach roads can be closed to motor vehicle traffic, while still allowing access for pedestrians and bicyclists. Roundabouts should be considered. Pedestrian refuges should be considered if the crossing distance exceeds approximately 40 feet. General use travel lanes and bike lanes may be striped with dashes to guide bicyclists and motorists through a long undefined area Corner Radii This intersection geometry feature has a significant impact on the comfort and safety of nonmotorized users. Small corner radii provide the following benefits: Smaller, more pedestrian-scale intersections resulting in shorter crossing distances. Slower vehicular turning speeds. Reduced pedestrian crossing distance and crossing time. Better geometry for installing perpendicular curb ramps for both crosswalks at each corner. Simpler, more appropriate crosswalk placement, in line with the approaching sidewalks. 63 Intersection Design

55 Figure 8. Tighter corner radii reduce crossing distance and slow turning traffic. (Credit: Michele Weisbart) When designing corner radii for Complete Streets, especially lower-speed residential streets, the passenger (P) vehicle is typically assumed as the default. Therefore, the default corner radius is 15 feet. Larger design vehicles should be used only where they are known to regularly make turns at the intersection, and corner radii should be designed based on the larger design vehicle traveling at crawl speed. In addition, designers should consider the effect that bicycle lanes and on-street parking have on the effective radius, increasing the ease with which large vehicles can turn. 64 Intersection Design

56 Figure 9. The effective corner radius controls turning speeds and the ability of large vehicles to turn. (Credit: Michele Weisbart) Limited duration encroachment and offtracking by large vehicles is acceptable onto multiple receiving lanes. When a design vehicle larger than the passenger (P) vehicle is used, the truck or bus should be allowed to turn into all available receiving lanes. Larger, infrequent vehicles (the control vehicle ) can be allowed to encroach on multiple departure lanes and partway into opposing traffic lanes. 65 Intersection Design

57 Figure 10. Corner radii can be kept smaller by allowing trucks and buses to turn into multiple receiving lanes. (Credit: Michele Weisbart) Curb Extensions Where on-street parking is allowed, curb extensions should be considered to replace a portion of the parking lane at crosswalks, thereby better defining and protecting permissible on-street parking spaces, and preventing encroachment on the intersection or crosswalks. Curb extensions should be the same width as the parking lane. The appropriate corner radius should be applied based on the guidance in the section above. Due to reduced road width, the corner radius on a curb extension may need to be larger than if curb extensions were not installed. Interference with bicycle or travel lanes or travel paths must be avoided. Curb extensions are usually not appropriate in the absence of on-street parking or excessive lane widths. 66 Intersection Design

58 In appropriate settings, curb extensions can provide benefits: Reduced pedestrian crossing distance resulting in less exposure to vehicles and shorter pedestrian clearance intervals at signals. Improved visibility between pedestrians and motorists. A narrowed roadway, which has a potential traffic calming effect. Additional room for street furniture, landscaping, and curb ramps. Slow down turning vehicles. Additional on-street parking potential due to improved sight lines at intersections. Since curb extensions allow pedestrians to walk out toward the edge of the parking lane without entering the roadway, pedestrians can better see vehicles and motorists can better see pedestrians, and the length of curbside available for parking can increase slightly in some cases. Curb extensions may impact other aspects of roadway design and operation: May impact street drainage and require catch basin relocation. May affect underground utilities. Can trigger loss of curbside parking, though careful planning often mitigates this potential loss, for example by relocating curbside fire hydrants, where no parking is allowed, to a curb extension. May complicate delivery access and garbage removal. May impact snow plows and street sweepers. May affect the turning movements of larger vehicles such as school buses, large fire trucks, and other service and delivery vehicles. Can complicate bike lanes or other bicycle treatments. 67 Intersection Design

59 Parked Vehicles Decrease Sight Distance Parked Setback for Sight Distance Curb Extension Improves Sight Distance Figure 11. Curb extensions improve sight distance between pedestrians and motorists, possibly allowing additional on-street parking. (Credit: Michele Weisbart) 68 Intersection Design

60 7.2.4 Crosswalk and Ramp Placement Crosswalks and ramps at intersections should be placed so they provide convenience and safety for pedestrians. The following recommended practices will help achieve these goals: Allow crossings on all legs of an intersection, unless there are no pedestrian accessible destinations on one or more of the corners. Closing a crosswalk usually results in a pedestrian either walking around several legs of the intersection, exposing them to more conflicts, or crossing at the closed location, with no clear path or signal indication as to when to cross. Provide marked crosswalks at signalized intersections. Allow for installation of pedestrian signal heads should future conditions warrant. Place crosswalks as close as possible to the desire line of pedestrians, which is generally in line with the approaching sidewalks. Provide as short as possible a crossing distance to reduce the time that pedestrians are exposed to motor vehicles; this is usually as close as possible to right angles across the roadway, except for skewed intersections. Ensure that there are adequate sight lines between pedestrians and motorists. This typically means that the crosswalks should not be placed too far back from the intersection. When a raised median is present, extend the nose of the median past the crosswalk with a cut-through for pedestrians. Provide one ramp per crosswalk (two per corner for standard intersections with no closed crosswalks). Ramps must be entirely contained within a crosswalk (the crosswalk can be flared to capture a ramp that cannot be easily relocated At intersections where roads are skewed or where larger radii are necessary for trucks, it can be difficult to determine the best location for crosswalks and sidewalk ramps. In these situations, it is important to balance the recommended practices above. Tighter curb radii make implementing the preceding recommendations easier, especially those associated with optimizing alignments, minimizing crossing distances, and enhancing sightlines. 69 Intersection Design

61 Figure 12. One curb ramp per crosswalk should be provided at corners. Ramps should align with sidewalks and crosswalks. (Credit: Michele Weisbart) On-Street Praking Near Intersections On-street parking should be positioned far enough away from intersections to ensure visibility of crossing pedestrians and approaching traffic. Curb extensions allow parking to be placed closer to the intersection Right-Turn Channelization Islands Right-turn lanes can increase the size of the intersection, the pedestrian crossing distance, and the likelihood of right-turns-on-red by inattentive motorists who do not notice pedestrians on their right. However, where there are heavy volumes of right turns (as determined by an engineering study), a right-turn lane may be the best solution to provide additional vehicle capacity without adding additional lanes elsewhere in the intersection. For turns onto roads with only one through lane and where truck turning movements are rare, providing a small corner radius at the right-turn lane often provides the best solution for pedestrians safety and comfort. 70 Intersection Design

62 At intersections of multi-lane roadways where trucks make frequent right turns, a raised channelization island between the through lanes and the right-turn lane is a good alternative to an overly large corner radius and enhances pedestrian safety and access. A channelization island is a triangular raised concrete platform between a right-turn lane and through lanes. They channelize vehicular traffic and provide a refuge for pedestrians crossing a roadway. If designed correctly, a raised island can achieve the following objectives: Allow pedestrians to cross fewer lanes at a time, by providing a refuge for staged crossing Allow motorists and pedestrians to judge the right turn/pedestrian conflict separately Reduce pedestrian crossing distance, which can improve signal timing for all users Balance vehicle capacity and truck turning needs with pedestrian safety Provide an opportunity for landscape and hardscape enhancement The following design practices for right-turn lane channelization islands should be used to provide safety and convenience for pedestrians, bicyclists, and motorists: Provide a yield sign for the slip lane and appropriate pavement markings Provide at least a 60-degree angle between vehicle flows, which reduces turning speeds and improves the yielding driver s visibility of pedestrians and vehicles Place the crosswalk across the right-turn lane about one car length back from where drivers yield to traffic on the other street, allowing the yielding driver to respond to a potential pedestrian conflict first, independently of the vehicle conflict, and then move forward, with no more pedestrian conflict These goals are best accomplished by creating an island that is roughly twice as long as it is wide. The corner radius will typically have a long radius (150 feet to 300 feet) followed by a short radius (20 feet to 50 feet). When creating this design, it is necessary to allow large trucks to turn into multiple receiving lanes. This design is often not practical for right-turn lanes onto roads with only one through lane. This right-turn channelization design is different from designs that provide free-flow movements (through a slip lane) where right-turning motorists turn into an exclusive receiving lane at high speed. Right turns should be signal-controlled in this situation to provide for a signalized pedestrian walk phase. 71 Intersection Design

63 Figure 13. Traffic channelization is an effective mitigation strategy when intersection radii reduction is not an option. (Credit: Michele Weisbart) Figure 14. Sharper angles of slip lanes are important to slow cars and increase visibility. (Credit: Michele Weisbart) 72 Intersection Design

64 7.3 Roundabouts In many circumstances, modern roundabouts can provide a safer, more cost-effective, and aesthetically pleasing intersection traffic control option. The distinctive features and characteristics of roundabout designs are summarized below. Users approach the intersection, slow down, stop and/or yield to pedestrians in a crosswalk, and then enter a circulating roadway, yielding to drivers already in the roundabout. The circulating roadway encircles a central island around which vehicles travel counterclockwise. Splitter islands at each approach leg force drivers to bear right. This deflection suppresses traffic speed, but allows movement by trucks. A landscaped visual obstruction in the central island obscures the driver s view of the road ahead, to discourage users from entering the roundabout at high speeds. Pedestrians are not allowed to access the central island, which should not contain attractions. The central island can vary in shape from a circle to a squarea-bout in historic areas, ellipses at odd shaped intersections, dumbbell, or even peanut shapes. Each leg of a roundabout has a triangular splitter island that serves several essential functions: Preventing drivers from turning left (the wrong-way ), Providing a refuge for pedestrians. Guiding drivers through the roundabout by directing them to the edge of the central island. Helping slow drivers (through deflection ). Roundabouts can range from quite small to quite large, from a central island diameter of about 12 feet for a traffic calming device at a neighborhood intersection to over 300 feet to the back of sidewalk on a large multi-lane roundabout. This section of the chapter briefly describes roundabout application and design information. For more detailed information, refer to NCHRP Report 672: Roundabouts: An Informational Guide, Second Edition. ( Advantages and Disadvantages Roundabouts reduce vehicle-to-vehicle and vehicle-to-pedestrian conflicts and, thanks to a substantial reduction in vehicle speeds, reduce all forms of crashes and crash severity. In particular, roundabouts eliminate the most dangerous and common crashes at signalized intersections: left-turn and right-angle crashes. Other benefits of roundabouts include the following: Pedestrians have to cross only one direction of traffic at a time. A smaller carbon footprint (no electricity is required for operation and fuel consumption is reduced as motor vehicles spend less time idling and don t have to accelerate as often from a dead stop). The opportunity to reduce the number of vehicle lanes between intersections (e.g., to reduce a five-lane road to a two-lane road, due to increased vehicle capacity at 73 Intersection Design

65 intersections). Little to no stopping during periods of low flow. Significantly reduced maintenance and operational costs because the only costs are related to the landscape and litter control. Reduced delay, travel time, and vehicle queue lengths. Lowered noise levels. Less fuel consumption and air pollution. Simplified intersections. Facilitated U-turns. The ability to create a gateway or a transition between distinct areas through landscaping. When constructed as a part of a new road or the reconstruction of an existing road, the cost of a roundabout is minimal and can be cheaper than the construction of an intersection and the associated installation of traffic signals and additional turn lanes. One drawback to roundabouts is that sight-impaired pedestrians can have difficulty navigating large roundabouts. This can be mitigated with ground level wayfinding devices and education for both drivers and pedestrians not familiar with roundabouts. Impacts on bicycles are mixed. While reduced conflicts and traffic speeds can benefit bicycle travel, many cyclists are uncomfortable traveling through roundabouts, and drivers unfamiliar with roundabouts might not be alert to the presence of bicyclists. Some treatments route bicycles around outside the roundabout, similar to pedestrians. Roundabouts may not be suitable in settings with heavy traffic and high pedestrian crossing volumes, since even at low speeds, a lack of gaps in traffic can generate excessive pedestrian delays. Conversely, persistent pedestrian interruptions can lock up traffic in a roundabout. In certain circumstances, roundabouts may require more land than corresponding conventional intersections, or simply may not fit the available land. Steep grades can also be a disqualifier. Proximity to a major signalized intersection with the potential to queue traffic into the roundabout is another situation to be avoided General Design Elements of Roundabouts CENTRAL ISLAND The design of the central island is an important element of a roundabout. In conjunction with well-designed approach and departure lanes, the central island controls vehicle speeds through deflection and controls the size of vehicles that can pass through and turn at a roundabout. It provides space for landscaping to beautify an intersection or create a focal point or community enhancement, but it also provides space for the inclusion of a vertical element such as a tree, which is important in providing long-range conspicuity of a roundabout. 74 Intersection Design

66 Figure 15. Single-lane roundabout. (Credit: Michele Weisbart) SPLITTER ISLANDS Splitter islands and/or medians on each approach serve several functions. Most importantly, they provide a refuge for pedestrians crossing at the roundabout, breaking the crossing into two smaller crossings. This allows pedestrians to select smaller gaps and cross more quickly. Splitter islands and medians direct vehicles toward the edge of the central island and limit the ability of drivers to make left turns the wrong way into the circulating roadway. Splitter islands should have a minimum width of 6 feet, and preferably 8 feet, from the face-of-curb to the opposite face-of-curb. TRUCK APRON Because central islands must be made large enough to deflect and hence control the speed of passenger vehicles, they can limit the ability of trucks to pass through or turn at a roundabout. To accommodate large vehicles, a truck apron (a paved, load-bearing area) is included around the edge of the central island. The truck apron is often paved with a fairly rough texture, can be decorative, and is raised enough to discourage encroachment by smaller high-speed passenger cars. The truck apron should be 3 inches high. 75 Intersection Design

67 PEDESTRIAN CROSSINGS Pedestrian crossings are located one car length away from the circulating roadway to shorten the crossing distance, separate vehicle-to-pedestrian conflicts from vehicle-to-vehicle conflicts, and allow pedestrians to cross between waiting vehicles. SIGNING AND MARKING Signing and marking should be in compliance with the current version of the MUTCD. For detailed design guidance on roundabouts, refer to the NCHRP Report 672, Roundabouts: An Informational Guide, Second Edition, However, care must be taken to not oversign roundabouts by including every sign allowed at roundabouts, except for needed directional signs; most roundabouts are designed so their function and use are self-explanatory Roundabout Design Criteria Before starting the design of a roundabout it is very important to determine the following: The number and type of lane(s) on each approach and departure as determined by a capacity analysis. The design vehicle for each movement. The presence of on-street bike lanes. The goal/reason for the roundabout, such as crash reduction, capacity improvement, speed control, or creation of a gateway or a focal point. Right-of-way and its availability for acquisition if needed. The existence or lack of sidewalks. The approach grade of each approach. Transit, existing or proposed. Truck volumes, or truck-route designation. Presence of on-street parking. 7.4 Pedestrian Crossings Appendix A of the Town of Leland Pedestrian Plan (December 2016) provides detailed design guidelines for pedestrian facilities, with special focus on intersections and crossings and on ADA accessibility. The following section highlights the fundamentals of good pedestrian crossing design; however, the Town of Leland Pedestrian Plan should be consulted for more detailed and comprehensive explanations related to appropriate applications and design dimensions for: Marked crosswalks Raised crosswalks Median refuge islands Curb radii and extensions 76 Intersection Design

68 ADA compliant curb ramps Signalization and pedestrian beacons Signage and pavement markings The following section provides an overview of planning and designing pedestrian crossings, along with additional details about some of the treatments discussed in the Town of Leland Pedestrian Plan. Figure 16. Curb extensions and median make crossing four-lane streets safer and more manageable. (Credit: Dan Burden) Principles of Pedestrian Crossing Design Walking requires two important features in the built environment: people must walk along streets and they must get across streets. Crossing a street should be easy, safe, convenient, and comfortable. While pedestrian behavior and intersection or crossing design affect the street crossing experience, motorist behavior (whether and how motorists stop for pedestrians) is the most significant factor in pedestrian safety. The following principles should be incorporated into every pedestrian crossing improvement: Pedestrians must be able to cross roads safely. Municipalities have an obligation to provide safe and convenient crossing opportunities. The safety of all street users, particularly more vulnerable groups, such as children, the elderly, and those with disabilities, and more vulnerable modes, such as walking and bicycling, must be considered when designing streets. Pedestrian crossings must meet accessibility standards and guidelines. Real and perceived safety must be considered when designing crosswalks crossing must 77 Intersection Design

69 be comfortable. A safe crossing that no one uses serves no purpose. Crossing treatments that have the highest crash reduction factors (CRFs) should be used when designing crossings. Safety should not be compromised to accommodate traffic flow. Good crossings begin with appropriate speed. In general, urban arterials should be designed to a maximum of 30 mph or 35 mph. Every crossing is different and should be selected and designed to fit its unique environment. The following issues should also be considered when planning and designing crossings: Ideally, uncontrolled crossing distances should be no more than 21 feet, and streets wider than 40 feet should be divided (effectively creating two streets) by installing a median or two crossing islands. The number of lanes should be limited to a maximum of three lanes per direction on all roads (plus a median or center turn lane). There should be a safe, convenient crossing at every transit stop. Avoid concurrent movements of motor vehicles and people at signalized intersections. Pedestrian signals should be provided at all signalized crossings where pedestrians are allowed High-Visibility Crosswalks Because of the low approach angle at which pavement markings are viewed by drivers, the use of longitudinal stripes in addition to or in place of transverse markings can significantly increase the visibility of a crosswalk to oncoming traffic. While research has not shown a direct link between increased crosswalk visibility and increased pedestrian safety, high-visibility crosswalks have been shown to increase motorist yielding and channelization of pedestrians, leading the Federal Highway Administration to conclude that high-visibility pedestrian crosswalks have a positive effect on pedestrian and driver behavior. Colored and stamped crosswalks should only be used at controlled locations. Staggered longitudinal markings reduce maintenance since they avoid vehicle wheel paths. 78 Intersection Design

70 Figure 17. Longitudinal crosswalk markings are more visible than lateral crosswalk markings. (Credit: Michele Weisbart) Figure 18. Typical crosswalk markings: Continental, Ladder, and Staggered Continental. (Credit: Michele Weisbart) Figure 19. Example of staggered continental crosswalk. (Credit: Michael Ronkin) 79 Intersection Design

71 7.4.3 Advanced Yield/Stop Lines Stop lines are solid white lines 12 to 24 inches wide, extending across all approach lanes to indicate where vehicles must stop in compliance with a stop sign or signal. Advance stop lines reduce vehicle encroachment into the crosswalk and improve drivers view of pedestrians. At signalized intersections, a stop line is typically set back between 4 and 6 feet. At uncontrolled crossings of multi-lane roads, advance yield lines can be an effective tool for preventing multiple threat vehicle and pedestrian collisions. Section 3B.16 of the MUTCD specifies placing advanced yield markings 20 to 50 feet in advance of crosswalks, depending upon location-specific variables such as vehicle speeds, traffic control, street width, on-street parking, potential for visual confusion, nearby land uses with vulnerable populations, and demand for queuing space. Thirty feet is the preferred setback for effectiveness at many locations. This setback allows a pedestrian to see if a car in the second (or third) lane is stopping after a driver in the first lane has stopped. Figure 20. Advanced yield markings. (Credit: Michele Weisbart) Figure 21. Example of advanced yield markings. (Credit: Sky Yim) Curb Extensions Curb extensions extend the sidewalk or curb line out into the parking lane, which reduces the effective street width. Curb extensions significantly improve pedestrian crossings by reducing the pedestrian crossing distance, visually and physically narrowing the roadway, improving the ability of pedestrians and motorists to see each other, and reducing the time that pedestrians are in the street. Reducing street widths improves signal timing since pedestrians need less time to cross. Motorists typically travel more slowly at intersections or mid-block locations with curb extensions, as the restricted street width sends a visual cue to slow down. Turning speeds are lower at intersections with curb extensions (curb radii should be as tight as is practicable). Curb extensions also prevent motorists from parking too close to the intersection. 80 Intersection Design

72 Curb extensions also provide additional space for two curb ramps and for level sidewalks where existing space is limited, increase the pedestrian waiting space, and provide additional space for pedestrian push button poles, street furnishings, plantings, bike parking and other amenities. A benefit for drivers is that extensions allow for better placement of signs (e.g., stop signs and signals). Curb extensions are generally only appropriate where there is an on-street parking lane. Where street width permits, a gently tapered curb extension can reduce crossing distance at an intersection along streets without on-street parking, without creating a hazard. Curb extensions must not extend into travel lanes or bicycle lanes. Figure 22. Curb extensions. (Credit: Michele Weisbart) Figure 23. Example of curb extensions. (Credit: Marcel Schmaedick) 81 Intersection Design

73 7.4.5 Lighting Lighting is important to include at all pedestrian crossing locations for the comfort and safety of the road users. Lighting should be present at all marked crossing locations. Lighting provides cues to drivers to expect pedestrians earlier. FHWA HT , The Information Report on Lighting Design for Mid-block Crosswalks, found that a vertical illumination of 20 lux in front of the crosswalk, measured at a height of 5 feet from the road surface, provided adequate detection distances in most circumstances. Although the research was constrained to mid-block placements of crosswalks, the report includes a brief discussion of considerations in lighting crosswalks co-located with intersections. The same principle applies at intersections. FHWA recommends that overhead lighting be placed feet in advance of crosswalks to prevent downcast shadows. Other good guidance on crosswalk lighting levels comes from the Illuminating Engineering Society of North America (IESNA) intersection guidance to illuminate pedestrians in the crosswalk to vehicles (see the adjacent image). Crosswalk lighting should provide color contrast from standard roadway lighting. Figure 24. Proper placement of crosswalk illumination. (Credit: Michele Weisbart) 82 Intersection Design

74 8 Bicycle Facilities Chapter 4 Bicycle Facility Standards and Guidelines from the 2008 Comprehensive Bicycle Plan for the Town of Leland describes in detail suitability criteria, signage and pavement markings, and dimensioning for the following types of bicycle facilities: Wide outside lanes Wide paved shoulders Bike lanes, including intersection treatments Shared-use paths (greenways) Bicycle crossings Bike Routes, including shared travel lanes and sharrows Bicycle parking Also addressed are bicycle safe drainage grates. 8.1 Principles of Bicycle Facility Design While Chapter 4 Bicycle Facility Standards and Guidelines should be the first resource for bicycle facility planning and design in the Town of Leland, principles for developing an appropriate and achievable network for bicycle travel are summarized below. Bicyclists should have safe, convenient, and comfortable access to all destinations. Every street is a bicycle street, regardless of bikeway designation. Street design should accommodate all types, levels, and ages of bicyclists. Bicyclists should be separated from pedestrians. 83 Bicycle Facilities

75 Bikeway facilities should take into account vehicle speeds and volumes, with Shared use on low volume, low-speed roads. Separation on higher volume, higher-speeds roads. Bikeway treatments should provide clear guidance to enhance safety for all users. Since most bicycle trips are short, a complete network of designated bikeways has a grid of roughly ½ mile. Bicyclists operate a vehicle and are legitimate road users, but they are slower and less visible than motor vehicles. Bicyclists are also more vulnerable in a crash than motorists. They need accommodation on busy, high-speed roads and at complex intersections. In congested urban areas, bicyclists provided with well-designed facilities can often proceed faster than motorists. Well-designed bicycle facilities guide cyclists to safely ride in the same direction as traffic and usually in a position 3 to 4 feet from the right edge of the traveled way or parked cars to avoid debris, drainage grates, and other potential hazards. Cyclists should be able to proceed through intersections in a direct, predictable, and safe manner. Bicycle infrastructure should use planning and designing options, from shared roadways to separate facilities, to accommodate as many user types as possible and to provide a comfortable experience for the greatest number of cyclists. For the purposes of these Guidelines, streets with operating speeds of 25 mph or less are typically considered suitable for shared use. Barring unusual circumstances, bicycles and motorized vehicles can share the same lane (with sharrows ) under such conditions Integrating Bicycles into the Street System Most bikeways are part of the street; therefore, well-connected street systems are very conducive to bicycling, especially those with a fine-meshed network of low-volume, low-speed streets suitable for shared roadways. In less well-connected street systems, where wide streets carry the bulk of traffic, bicyclists need supplementary facilities, such as short sections of paths and bridges, to connect otherwise unconnected streets. There are no hard and fast rules for when a specific type of bikeway should be used, but some general principles guide selection. As a general rule, as traffic volumes and speeds increase, greater separation from motor vehicle traffic is desirable. Other factors to consider are users (more children or recreational cyclists may warrant greater separation), adjacent land uses (multiple driveways may cause conflicts with shared-use paths), available right-of-way (separated facilities require greater width), and costs. There are occasions when it is infeasible or impractical to provide bikeways on a busy street, or the street does not serve the mobility and access needs of bicyclists. The following guidelines should be used to determine if it is more appropriate to provide facilities on a parallel local street: Conditions exist such that it is not economically or environmentally feasible to provide adequate bicycle facilities on the street. 84 Bicycle Facilities

76 The street does not provide adequate access to destination points within reasonable walking distances, or separated bikeways on the street would not be considered safe. The parallel route provides continuity and convenient access to destinations served by the street. Costs to improve the parallel route are no greater than costs to improve the street. If any of these factors are met, cyclists may prefer the parallel local street facility in that it may offer a higher level of comfort (bicycle boulevards are based on this approach). Off-street paths can also be used to provide transportation in corridors otherwise not served by the street system, such as along rivers and canals, through parks, along utility corridors, on abandoned railroad tracks, or along active railroad rights-of-way. While paths offer the safety and scenic advantages of separation from traffic, they must also offer frequent connections to the street system and to destinations such as residential areas, employment sites, shopping, and schools. Street crossings must be well designed with measures such as signals or median refuge islands Bicycle Boulevards One potentially-relevant type of bicycle facilities not included in Chapter 4 Bicycle Facility Standards and Guidelines is the bicycle boulevard. A bicycle boulevard is an enhanced shared roadway; a local street is modified to function as a prioritized through street for bicyclists while maintaining local access for automobiles. This is done by adding trafficcalming devices to reduce motor vehicle speeds and through trips, and installing traffic controls that limit conflicts between motorists and bicyclists and give priority to through bicyclist movement. One key advantage of bicycle boulevards is that they attract cyclists who do not feel comfortable on busy streets and prefer to ride on lower traffic streets. Bicycle travel on local streets is generally compatible with local land uses (e.g., residential and some retail). Residents who want slower traffic on neighborhood streets often like measures that support bicycle boulevards. By reducing traffic and improving crossings, bicycle boulevards also improve conditions for pedestrians. Successful bicycle boulevard implementation requires careful planning with residents and businesses to ensure acceptance. A successful bike boulevard includes the following design elements: Selecting a direct and continuous street, rather than a circuitous route that winds through neighborhoods. Bike boulevards work best on a street grid. If any traffic diversion will likely result from the bike boulevard, selecting streets that have parallel higher-level streets can prevent unpopular diversion to other residential streets. Placing motor vehicle traffic diverters at key intersections to reduce through motor vehicle traffic (diverters are designed to allow through bicyclist movement). Turning stop signs towards intersecting streets, so bicyclists can ride with few interruptions. Replacing stop-controlled intersections with mini-circles and mini-roundabouts to reduce the number of stops cyclists must make. Placing traffic-calming devices to lower motor vehicle traffic speeds. 85 Bicycle Facilities

77 Placing wayfinding and other signs or markings to route cyclists to key destinations, to guide cyclists through difficult situations, and to alert motorists of the presence of bicyclists. Where the bike boulevard crosses high-speed or high-volume streets, providing crossing improvements such as: Signals, where a traffic study has shown that a signal will be safe and effective. To ensure that bicyclists can activate the signal, loop detection should be installed in the pavement where bicyclists ride. Roundabouts where appropriate. Median refuges wide enough to provide a refuge (8 feet minimum) and with an opening wide enough to allow bicyclists to pass through (6 feet). The design should allow bicyclists to see the travel lanes they must cross. 86 Bicycle Facilities

78 9 Streetscape The street is a system: a transportation system, an ecosystem, and a system of social and economic interactions. The idea of a streetscape is to build an interconnected system to sustainably enhance the local environment, its resources, the community, and the local economy. The elements described in this section should be integrated with the components of the travelway detailed in previous sections to maximize ecological, economic, and social benefits. No individual street project should be pursued in a vacuum, but rather planned as part of a comprehensive strategy. Medians, roundabouts, curb extensions, and other road configurations provide viable space for people and nature. They provide opportunities for spaces with vegetation, stormwater management tools, and other streetscape elements like benches and bike racks. A good overall reference for streetscape appearance is the 2015 NCDOT Aesthetics Guidance Manual. It compiles a comprehensive summary of relevant policies, resources, and guidelines that go beyond aesthetics to integrate safety, sustainability, and functionality. Focus areas address roadways, roadside environment, landscapes, stormwater, bicycle and pedestrian infrastructure, and other aspects of integrated design. 9.1 Stormwater Management Stormwater regulations for the Town of Leland are found in Chapter 32 - Phase II Stormwater Ordinance of the Code. An overview of Best Management Practices (BMPs) for sustainable stormwater management is provided in this section of the Street Design Guidelines. The street is a constructed waterway, often differing from the natural path of water and disconnected from the hydrologic cycle. Traditional design has focused on speedy removal of 87 Streetscape

79 water from the street and disposal of it as waste in storm drains and sewers. This section provides tools to reclaim stormwater as a resource and allow it to nourish trees and soils on its path to ground or surface waters. While conventional stormwater controls aim to move water off-site and into storm drains as quickly as possible, stormwater management seeks to use and store water on-site for absorption and infiltration in order to clean it naturally and use it as a resource. The storm drain system, therefore, is an overflow support system rather than a primary conveyance system. Stormwater management deals with water as an amenity rather than a liability. Many of the stormwater management options discussed in this section can and should integrate easily with traffic calming measures installed along streets, such as boulevard islands, rotary islands, traffic circles, street ends, chicanes, and curb extensions. These elements can easily incorporate stormwater treatment into the landscape and stormwater tools can be made more cost-effective if integrated early in the design process. Stormwater management also provides opportunities to leverage other streetscape elements and components of living streets. A strategic plan linking streetscape elements and street design can maximize benefits Goals and Benefits of Stormwater Management The primary goals of stormwater management are as follows: Reduce limit the amount of impervious surfaces that generate additional runoff. Slow friction slows flow Spread allow water to be slowed enough to infiltrate. Sink keep water on site. Store contain water for direct non-potable/potable indoor/outdoor purposes. Use to irrigate and replace imported potable water. These goals can be expressed succinctly: slow it, spread it, store it, and sink it, but use it. The tools provided in this section enable cities to attain regulatory compliance and provide the following ecological, economic, and aesthetic benefits: Reduced use of potable water for irrigation Reduced surface water pollution Support for the urban ecosystem and wildlife habitat Enhanced flood control Biological filtration and bioremediation Groundwater recharge Reduced heat island effect 88 Streetscape

80 Education through best management practices (BMP) visibility Aeration of root zone Potential reductions in stormwater infrastructure and treatment costs Improved aesthetics and public space within neighborhoods Principles of Stormwater Management Use the conventional storm drain system as the overflow approach, not the primary system to manage stormwater. Wherever possible, natural drainages should be the primary overflow. Harvest, use, and/or store stormwater as close to its source as possible. Wet weather rainfall and its byproduct, stormwater, can offset or eliminate imported potable irrigation water needs when harvested and used on-site. Harvesting and storing stormwater transforms a flooding liability into an on-site irrigation resource. This ensures natural waterways and their plant communities have local sources of water, thereby reducing the need for imported water. Harvesting and storing rainwater also reduces the need for costly drainage conveyance infrastructure for stormwater management. Select tools that mimic natural processes. Minimize the cost of the installation and maintenance by using gravity flow rather than pumped flow, living filtration over synthetic/mechanical filtration, and living surface infiltration instead of piped drainage. Priority should also be given to pervious versus impervious surfaces. The primary purpose is to harvest and utilize rain as part of a healthy vegetated watershed. For example, vegetation can reduce runoff water volume and pollutant load, provide summer shade and cooling, and enhance wildlife habitat and sense of place with native vegetation rooted to the local ecosystem. Maximize stormwater management by integrating it into the myriad design elements in the public right-of-way. The water system is part of a larger, interconnected system. Maximize the benefits of stormwater strategies. For example, traffic calming and road diets can double as stormwater harvesting strategies. In addition, use vegetation to make streets better places and use stormwater management as an integral element of the urban forest. Show the water flow. The benefits of stormwater management are ecological, economic, and social. Make the functions described in this section visible for street users to see, understand, appreciate, and replicate. Public right-of-way stormwater installations can inspire private property installations and serve as model installations for neighborhoods. Visible water flow systems are also easier to maintain. Blockages are easier to notice and easier to access for regular maintenance Definitions The following terms describe the elements and techniques of sustainable stormwater management: Best Management Practice (BMP). Operating methods and/or structural devices used to reduce stormwater volume, peak flows, and/or pollutant concentrations of stormwater 89 Streetscape

81 runoff through one or more of the following processes: evapotranspiration, infiltration, detention, filtration, and biological and chemical treatment Bioretention. A soil and plant-based retention practice that captures and biologically degrades pollutants as water infiltrates through sub-surface layers containing microbes that treat pollutants. Treated runoff is then slowly infiltrated and recharges the groundwater. These biological processes operate in all infiltration-based strategies, including various retention systems. Conveyance. The process of water moving from one place to another. Daylight. To bring stormwater flow to the surface, exposed to open air and visible to the public Design Storm. A storm whose magnitude, rate, and intensity do not exceed the design load for a storm drainage system or flood protection project Detention. Stormwater runoff that is collected at one rate and then released at a controlled rate. The difference is held in temporary storage. Dry weather runoff. Human activity-related sources of water, such as irrigation overspray, car wash runoff, leaking plumbing, fire hydrant and well flushing, and runoff from mechanical processes such as air conditioning Filtration. A treatment process that allows for removal of solid (particulate) matter from water by means of porous media such as sand, soil, vegetation, or a man-made filter. Filtration is used to remove contaminants. Hardscape. Impermeable surfaces, such as concrete or stone, used in the landscape environment along sidewalks or in other areas used as public space. Infiltration. The process by which water penetrates into soil from the ground surface. Permeability/Impermeability. The quality of a soil or material that enables water or air to move through it, and thereby determines its suitability for infiltration-based stormwater strategies. Retention. The reduction in total runoff that results when stormwater is diverted and allowed to infiltrate into the ground through existing or engineered soil systems. Runnel. Narrow, shallow drainage channel designed to carry small amounts of runoff. Runoff. Water from rainfall that flows over the land surface that is not absorbed into the ground. Sedimentation. The deposition and/or settling of particles suspended in water as a result of the slowing of the water. Softscape. Natural, permeable, landscape surfaces such as vegetation, mulch, and loose rock. Stormwater. Rainwater that flows and collects in the street. 90 Streetscape

82 9.1.4 Tools for Stormwater Management There are many tools and best management practices (BMPs) for managing stormwater sustainably. Most popular are devices and practices that encourage water percolation on-site to the maximum degree practicable (given soil conditions, pollutant levels, etc.). The most important devices and practices are bioretention BMPs consisting of swales, planters, and vegetated buffer strips, as well as detention BMPs consisting of rain gardens, infiltration trenches, and dry wells. While permeable paving also slows and retains stormwater, its primary function is as a surfacing material that reduces runoff. Additional tools include delivery and conveyance tools and inlet protections. These stormwater management tools are highly customizable and can be integrated into a variety of different types of spaces in any of the street types. They can be implemented alone or in concert with one another to achieve cumulative benefits. Opportunity sites include medians, corner and midblock curb extensions, roadway and park edges, front building edges, and surrounding street trees. Selecting the appropriate BMP is very dependent on street type and site conditions. High traffic commercial streets have different parameters than smaller residential streets Site Considerations Streetscape geometry, topography, and climate determine the types of controls that can be implemented. The initial step in selecting a stormwater tool is determining the available open space and constraints. Although the maximum size of a selected stormwater facility may be determined by available area, the standard design storm should be used to determine the appropriate size, slope, and materials of each facility. After identifying the appropriate stormwater facilities for a site, an integrated approach using several tools is encouraged. To increase water quality and functional hydrologic benefits, several stormwater management tools can be used in succession. This is called a treatment train approach. The control measures should be designed using available topography to take advantage of gravity for conveyance to and through each facility Bioretention Bioretention is a stormwater management process that cleans stormwater by mimicking natural soil filtration processes as water flows through a bioretention BMP. It incorporates mulch, soil pores, microbes, and vegetation to reduce and remove sediment and pollutants from stormwater. Bioretention is designed to slow, spread, and, to some extent, infiltrate water. Each component of the bioretention BMP is designed to assist in retaining water, evapotranspiration, and adsorption of pollutants into the soil matrix. As runoff passes through the vegetation and soil, the combined effects of filtration, absorption, adsorption, and biological uptake of plants remove pollutants. For areas with low permeability or other soil constraints, bioretention can be designed as a flow-through system with a barrier protecting stormwater from native soils. Bioretention areas can be designed with an underdrain system that directs the treated runoff to infiltration areas, cisterns, or the storm drain system, or may treat the water exclusively through surface flow. 91 Streetscape

83 Bioretention facilities can be included in the design of all street components: adjacent to the traveled way and in the frontage or furniture sidewalk zones. They can be designed into curb extensions, medians, traffic circles, roundabouts, and any other landscaped area. Depending on the feature, maintenance and access should always be considered in locating the device. Bioretention systems are also appropriate in constrained locations where other stormwater facilities requiring more extensive subsurface materials are not feasible. Swales, planters, and vegetated buffer strips are examples of bioretention devices or treatments Detention Detention devices differ from retention in that they are designed and sized to hold a specific volume of water and then slowly release it over time. The objective of bioretention is to improve the quality of stormwater by promoting filtration and adsorption as water flows through vegetation and soil. Detention devices do not function as flow-through features, but rather the objective is to collect and contain water until it is removed by controlled release or infiltrated into the soil. Overflow outlets may be included to manage large storm events. Pollutants may be removed by vegetation and the topsoil layer as in bioretention BMPs so that stormwater is treated before it is infiltrated. Detention devices can greatly reduce the volume of runoff from streetscapes and for small storm events may completely eliminate runoff. Rain Gardens Rain gardens are vegetated depressions in the landscape. They have flat bottoms and gently sloping sides. Rain gardens can be similar in appearance to swales, but their footprints may be any shape. Rain gardens hold water on the surface, like a pond, and have overflow outlets. The detained water is infiltrated through the topsoil and subsurface drain rock unless the volume of water is so large that some must overflow. Rain gardens can reduce or eliminate off-site stormwater discharge while increasing on-site recharge. Figure 25. Rain garden detail. (Credit: Julia Campbell and Michele Weisbart) 92 Streetscape

84 Infiltration Trenches and Dry Wells Infiltration trenches are linear, rock-filled features that promote infiltration by providing a high ratio of sub-surface void space in permeable soils. They provide onsite stormwater retention and may contribute to groundwater recharge. Infiltration trenches may accept stormwater from sheet flow, concentrated flow from a swale or other surface feature, or piped flow from a catch basin. Because they are not flow-through BMPs, infiltration trenches do not have outlets but may have overflow outlets for large storm events. Figure 26. Infiltration trench. (Credit: Julia Campbell and Michele Weisbart) Dry wells are typically distinguished from infiltration trenches by being deeper than they are wide. They are usually circular, resembling a well, and are backfilled with the same materials as infiltration trenches. Dry wells typically accept concentrated flow from surface features or from pipes and do not have outlets. Infiltration trenches and dry wells typically have small surface footprints so they are potentially some of the most flexible elements of landscape design. However, because they involve subsurface excavation, these features may interfere with surrounding structures. Care needs to be taken to ensure that surrounding building foundations, pavement bases, and utilities are not damaged by infiltration features. Once structural soundness is ensured, infiltration features may be located under sidewalks and in sidewalk planting strips, curb extensions, roundabouts, and medians. When located in medians, they are most effective when the street is graded to drain to the median. Dry wells require less surface area than trenches and may be more feasible in densely developed areas. Prior to design of any retention or infiltration system, proper soil investigation and percolation testing should be conducted to determine appropriate infiltration design rates. Any site with potential for previous underground contamination should be investigated. Infiltration trenches and dry wells can be designed as stand-alone systems when water quality is not a concern or may be combined in series with other stormwater tools. Infiltration features do not treat stormwater and may become damaged by stormwater carrying high levels of sediment. In general, infiltration features should be designed in series with bioretention tools unless the infiltration features receive water from well-vegetated areas where sediment is not expected. Pre-treatment features should be designed to treat street runoff prior to discharging to infiltration features. Bioretention devices, sumps, and sedimentation basins are several pre-treatment tools effective at removing sediment. 93 Streetscape