TABLE OF CONTENTS. 1.0 Introduction Purpose Goals Policies Responsibility Cost Toolbox...

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3 TABLE OF CONTENTS 1.0 Introduction Purpose Goals Objectives Policies Responsibility Cost Toolbox Passive Traffic Calming Measures Vertical Traffic Calming Measures Horizontal Traffic Calming Measures Not Traffic Calming Measures Alternatives to Traffic Calming Measures Traffic Management Conceptual Drawings Forms Used to Request Traffic Calming

4 1.0 INTRODUCTION The City of Oak Hill is a community incorporated in 1952 that consists primarily of residential zoning. The City is home to approximately 4,700 residents and 1,850 homes. While located within the boundaries of the Metropolitan Government of Nashville and Davidson County, the City maintains the public road network within the City boundaries. The City has approximately 49 miles of road, and is comprised of approximately 8 square miles of land. Previously, the City did not have standard protocol for responding to citizen complaints or traffic calming requests. The few existing traffic calming measures in the City that have been installed are in close proximity to schools. This was the loose standard for traffic calming measures, that the City would only consider them near schools. The City decided that a more standard protocol was needed to appropriately respond to the requests for traffic calming measures. The City of Oak Hill traffic calming program provides a process to respond to residents concerns regarding speeds, safety, noise, and overall quality of life related to vehicular traffic on neighborhood streets. This handbook documents the goals and objectives of traffic calming, the request process for residents and the City to follow, and design guidelines for traffic calming measures. The mission of the City of Oak Hill is to preserve its natural resources and residential environment; to offer an enhanced level of services to its citizens; and to provide a strong sense of community pride with historical awareness all within close proximity to a world-class metropolitan area. The role of this traffic calming program is to combine the mission of the City and the desire for sensible traffic calming measures. 2

5 2.0 PURPOSE Speeding A typical concern of residents is speeding along their neighborhood streets. The motorists that exceed the posted speed limit along neighborhood streets often include neighborhood residents and nonresidents that use the City of Oak Hill as a cut through. While some motorists exceed the posted speed limit because they are irresponsible drivers, other motorists simply find themselves invited to exceed the posted speed limit because of the road s design features. These features can include excessively wide pavement, straight sections of the road, and the absence of landscaping. Speeding vehicles also portray the feeling that the street is dedicated to the motorist, instead of a multi-modal link that unifies the neighborhood. Cut Through Traffic Traffic is defined as cut through if neither the origin nor the destination is within the neighborhood. A motorist is considered cut through if he/she drives through the neighborhood on local streets, but has no relationship with the neighborhood itself. This traffic should be using arterial and collector streets. Unfortunately, motorists sometimes use neighborhood streets to avoid congestion on arterials and collector streets. These motorists travel through the community in order to shorten driving distances, decrease travel times, or avoid traffic signals. Safety Excessive traffic speeds can threaten a neighborhood s feeling of safety. Residents may develop concerns about walking or biking on the street. Rather than allowing the street to be controlled by speeding vehicles, traffic calming provides a route for residents of the neighborhood to consider their streets as multimodal links. Aesthetics Traffic calming provides the opportunity to transform the streets into aesthetically pleasing infrastructure. Traffic calming measures, while serving the primary purpose, can also improve the landscaping and provide a gateway/landmark within the neighborhood. When selecting a traffic calming measure for a specific location, emphasis should be placed on the ability to improve overall aesthetics of the area. 3

6 3.0 GOALS The goal for this traffic calming program is to improve the overall quality of life for its residents by: Reducing vehicular speeds Discouraging cut through traffic Improving real and perceived safety Improving neighborhood streets Traffic calming has the ability to provide solutions for cut-through traffic, speeding, safety, and aesthetics. However, engineering solutions will not produce sufficient results by themselves. Successful traffic calming applies the Three E s: Education, Enforcement, and Engineering. Education It is essential that residents and neighbors understand the need to obey the posted speed limit. When there is a perceived speeding problem within the neighborhood, the residents themselves are commonly contributing to this problem. Education can occur by reminding motorists of the potential risk to the neighborhood children and adults; this can be done by means ranging from newsletters and brochures to s and social media. Additionally, general education on the traffic calming program can improve the neighborhood s understanding of possible solutions. Enforcement Police officers are the usual source for increased enforcement of traffic laws. Law enforcement can monitor vehicular speeds and the observance of stop signs, issuing citations in response to violations. However, neighborhood volunteers can also be an effective tool to enforce the traffic laws. A temporary police presence results in temporary improvements, as motorists are more likely to exceed posted speed limits in the absence of police officers. However, random police presence can have a continuous benefit as long as the random enforcement continues. The temporary placement of a radar trailer or a dynamic speed display sign can also be used to inform motorists of the speed they are traveling compared to the posted speed limit. Engineering Through proper engineering the roadway can be physically modified in some manner, with the purpose of encouraging a change in motorist behavior by reducing speed, increasing awareness of pedestrians and bicyclists, or diverting traffic to a more appropriate street (arterial or collector). Engineering solutions are intended to be self-enforcing and should be considered after education and enforcement activities have been performed. Sound engineering judgment should be used for any proposed modification of a neighborhood roadway involving traffic calming measures, installation of new signage, and additional pavement markings. 4

7 4.0 OBJECTIVES The overall objectives of the City of Oak Hill traffic calming program are as follows: 1. Encourage citizen involvement in the traffic calming program. 2. Maintain and improve the residents quality of living in the City through reductions in vehicular speed and cut-through traffic. 3. Minimize the adverse impact of causing traffic to divert from one street to another. 4. Effectively balance traffic calming needs with emergency vehicle responsiveness. 5. Maintain and improve the safety for all modes of transportation on City streets. The City supports these objectives through establishing traffic calming policies. Emergency Vehicle Response should be considered when developing traffic calming solutions. Fire departments usually have the most concerns due to the potential difficulties negotiating the long wheel base of fire trucks around or over traffic calming measures. Therefore, the City will consult with the emergency responders (Nashville Fire Department and Metropolitan Nashville Police Department) prior to the installation of a traffic calming project to help alleviate these concerns. Maintenance Costs may arise from the installation of traffic calming measures, especially if additional landscaping is included. An agreement should be developed between the City and residents to determine who is responsible for these maintenance costs. A separate agreement can be developed for each individual project, or an overall agreement can be created that encompasses all traffic calming in the City. One alternative that decreases maintenance costs is a policy called xeriscaping. Xeriscaping refers to landscaping techniques that reduce or remove the need for additional water from irrigation. Non-Motorized Users include pedestrians and bicyclists. Traffic calming measures such as vertical obstacles and roundabouts can cause an inconvenience for the alternative modes of transportation. Bicyclists may experience more challenges in traversing a vertical traffic calming measure; roundabouts do not require vehicles to always stop, and therefore may provide fewer gaps for pedestrians to cross the street. However, proper design solutions can be included to alleviate these challenges for pedestrians and bicyclists. Advance signing and marking can help communicate to a bicyclist that a vertical obstruction is ahead. Any roundabout design should include splitter islands that separate the traffic directions on the intersection approaches; these splitter islands can also provide a pedestrian refuge while crossing the street. Parking Issues may result from traffic calming measures if off-street parallel parking is restricted or removed. City ordinance allows vehicles to park adjacent to the roadway as long as each tire of the vehicle is off the roadway. Some traffic calming measures may be accompanied by curb and gutter, which is not designed for vehicles to traverse. The installation of curb and gutter would therefore restrict the locations along private property frontage that could be used for off-street parallel parking. The residents in the traffic calming study area (impact area) should be advised of the possible restrictions to off-street parallel parking at the neighborhood meeting(s). 5

8 FLOW CHART (This is an illustration of the Policies described in Section 5.0) Traffic Calming Request Determine Impact Area 25% Approval YES Traffic Calming Petition 25% Approval NO No Consideration For 6 Months Collect Data Volume, Speed, Other YES Evaluate Data Proceed? NO No Consideration For 12 Months Legend Citizen Decision Prepare Concept Plan and Opinion of Probable Cost City Decision Meet with Neighborhood Citizen and/or City Task Finalize Concept Plan Consequence of A No Result 75% Approval YES Traffic Calming Ballot 75% Approval NO No Consideration For 12 Months Prepare Design Plans Complete Construction YES Evaluate Results Success? NO Consider Modification Or Removal Finished 6

9 5.0 POLICIES GENERAL INFORMATION: 1. This general information applies to the traffic calming review process within the City of Oak Hill. 2. The City of Oak Hill in the State of Tennessee is considered the City. 3. The traffic calming review process is initiated once the City has received a completed Traffic Calming Request Form. The property owner who submits the Traffic Calming Request Form is considered the citizen representative. 4. The study area during the traffic calming review process is considered the impact area. 5. Owners of land parcels within the impact area are considered property owners. 6. Land parcels within the impact area will be restricted to one (1) property owner during decision-making steps (e.g. petition signature, yes/no vote, approve/disapprove vote). a. Only one (1) person may perform a decision-making step for a property address. i. If more than one (1) person from the same property address performs a decisionmaking step, and the results are unanimous, the signature/vote will be included and recorded as one (1) for that property address. ii. If more than one (1) person from the same property address performs a decisionmarking step, and the results are conflicting, all signatures/votes will be discarded and omitted for that property address. b. For properties with single-family residential homes, decisions shall be made by a property owner who is listed on the property deed. c. For properties with multi-family residential homes (e.g. duplex), decisions shall be made by a property owner who is listed on the property deed. d. Renters may be partially involved in the traffic calming review process. However, renters shall not be involved during decision-making steps. e. For properties with a church and/or school, decisions shall be restricted to one (1) person employed at or designated by the church and/or school. 7. All days refer to calendar days. 8. The Traffic Calming Program Handbook will be used to modify existing roadways by implementing traffic calming measures; this Handbook will not be used to construct new roadways, sidewalks, or bicycle paths. ELIGIBILITY: 1. The City shall only consider traffic calming measures along a roadway within the City boundary. The City may consider traffic calming measures along a roadway that is partially within the City boundary; however, only the section of roadway that is located within the City boundary will be considered. 2. Traffic calming measures shall not be considered along the following five (5) roadways: Franklin Pike, Granny White Pike, Battery Lane/Harding Place, Tyne Boulevard, and Hogan Road. a. These roadways are omitted because they are classified as either arterials or collectors by the Tennessee Department of Transportation. b. Measures included in the Toolbox of this Traffic Calming Program Handbook may be considered and implemented on these five (5) roadways; however, the policies within this Traffic Calming Program Handbook will not apply. 7

10 8 FORMS: 1. Traffic Calming Request - Installation 2. Traffic Calming Petition - Installation 3. Traffic Calming Ballot - Installation 4. Traffic Calming Request - Removal 5. Traffic Calming Petition - Removal 6. Traffic Calming Ballot - Removal PROCESS: 1. Request 2. Petition 3. Evaluation 4. Ballot 5. Design and Construction 6. Post-Implementation 7. Removal (if applicable) 8. Request Initiated by the City REQUEST: 1. The Traffic Calming Request is available upon request and/or via the City website. 2. The traffic calming review process shall be initiated once the City has received the completed Traffic Calming Request. 3. The Traffic Calming Request shall be completed by the citizen representative. Signatures are required from two (2) additional property owners along the same roadway within 1,000 feet of the property owned by the citizen representative submitting the request. 4. The City shall review the Traffic Calming Request and establish the impact area. This impact area will typically be determined using the information included in the request, discussions between the City and property owners, and existing information about the roadway. a. The impact area will typically include the property on both sides of the roadway extending to the nearest traffic signal, stop sign, or intersection with a public road. b. The impact area may also include adjacent roadways if it is determined that traffic calming measures may divert traffic onto adjacent roadways. c. The impact area boundaries may be modified based upon City judgment. PETITION: 1. The City shall prepare and distribute the Traffic Calming Petition to the citizen representative. The citizen representative is responsible for obtaining signatures from property owners within the impact area. The petition shall be completed and returned to the City. 2. An Application Fee may be required by the City in conjunction with submittal of a Traffic Calming Petition. 3. The evaluation for traffic calming measures along a roadway shall be initiated once the City has received the completed Traffic Calming Petition. 4. The City shall allow twenty-eight (28) days for the petition to be returned. Day zero (0) is the date on which the City delivers the Traffic Calming Petition to the citizen representative.

11 5. A minimum of twenty-five (25) percent of property owners within the impact area must indicate their approval by signing the Traffic Calming Petition. a. If petition approval is achieved, the evaluation phase begins. b. If twenty-eight (28) days elapse and petition approval has not been achieved, the roadway will not be considered for traffic calming for six (6) months. This six (6) month waiting period may be waived at the discretion of the City. EVALUATION: 1. The City may choose to employ passive traffic calming measures during the evaluation phase. These measures may occur in conjunction with or in lieu of the evaluation phase. Passive traffic calming measures can include targeted speed limit enforcement, dynamic speed display sign placement, and/or radar trailer placement. If an additional study is performed that determines the passive measures have been successful, the City will present the results to the citizen representative. This may represent justification for not proceeding further with the evaluation phase. 2. The City shall collect information and data along roadway(s) in the project as deemed necessary by the City. This data collection may include any of the following: a. Volume count to determine peak hour traffic b. Volume count to determine 24-hour traffic c. Speed study to determine existing speed data d. Classification count to determine heavy vehicle traffic e. Crash data for the most recent three (3) years f. Study to quantify cut-through traffic g. Existing roadway conditions (e.g. pavement condition, signing, marking, sidewalk) h. Other information/data that may be applicable to the roadway(s) 3. The following criteria shall be considered during the evaluation: a. The peak hour traffic volume should be a minimum of 60 vehicles per hour and a maximum of 300 vehicles per hour. If the peak hour traffic volume is smaller than the minimum or larger than the maximum, traffic calming measures shall not be considered along the roadway. b. The average 24-hour traffic volume should be a minimum of 600 vehicles per day and a maximum of 3,000 vehicles per day. If the average 24-hour traffic volume is smaller than the minimum or larger than the maximum, measures shall not be considered along the roadway. c. The 85th percentile speed along the roadway should be a minimum of five (5) miles per hour above the posted speed limit. If the 85th percentile speed is smaller than the minimum, traffic calming measures shall not be considered along the roadway. d. The roadway grade should be a maximum of eight (8) percent. If the roadway grade is larger than this maximum, traffic calming measures shall not be considered along the roadway. 4. The City will perform the evaluation and, if traffic calming measures are justified by the data and criteria set forth herein, develop a concept plan. This concept plan will specify the type, number, and location of the proposed traffic calming measures. The study will also identify the advantages, disadvantages, and an opinion of probable cost. 9

12 5. The City will, if needed, modify the impact area based on the concept plan. The impact area may be modified based upon City judgment. 6. A neighborhood meeting shall then occur between the City and property owners located within the impact area. The purpose of this meeting is to discuss the preliminary concept plan and receive feedback. 7. The concept plan will be revised, if needed, following the neighborhood meeting. This will result in the final concept plan. 8. If traffic calming measures are not justified by the data and criteria set forth herein, the roadway will no longer be considered for traffic calming. The roadway will not be considered for traffic calming for twelve (12) months. This twelve (12) month waiting period may be waived at the discretion of the City. BALLOT: 1. The impact area for the Traffic Calming Petition may differ from the impact area for the Traffic Calming Ballot. 2. The City shall prepare and distribute the Traffic Calming Ballot to property owners within the impact area. The ballots shall be completed and returned to the City. 3. The City shall allow twenty-eight (28) days for the ballots to be returned. Day zero (0) is the date on which the City delivers the Traffic Calming Ballot to the citizen representative. 4. A minimum of seventy-five (75) percent of property owners within the impact area must indicate their support on the Traffic Calming Ballot. a. If ballot approval is achieved, the design and construction phase may begin. b. If ballot approval is not achieved, the roadway will no longer be considered for traffic calming. The roadway will not be considered for traffic calming for twelve (12) months. This twelve (12) month waiting period may be waived at the discretion of the City. DESIGN AND CONSTRUCTION: 1. The City shall be responsible for the design and engineering plans of the traffic calming measures. 2. Construction of the traffic calming project shall proceed upon approval of the design and engineering plans, and once funds are available for project completion. 3. The property owners shall be responsible for funding the construction of the traffic calming project. POST-IMPLEMENTATION: 1. The City shall collect post-implementation information and data along the roadway(s) in the project. This data collection shall occur between ninety (90) and one hundred and twenty (120) days following completion of construction. The purpose of this effort is to determine whether the objectives for traffic calming have been satisfied along the roadway(s). 2. If the City determines that the objectives have been satisfied, then the project is considered complete. 3. If the City determines that the objectives have not been satisfied, then the City has the option to modify or remove the traffic calming measures. If this option is pursued, the traffic calming review process would follow the same guidelines beginning with the evaluation phase. 10

13 REMOVAL: 1. This phase of the traffic calming review process only applies when the property owners desire removal of existing traffic calming measures. 2. The property owners within the impact area shall have the ability to request removal of traffic calming measures. 3. The property owners within the impact area must wait a minimum of twelve (12) months after completion of the traffic calming measure installation. 4. The same policies and procedures for the installation of traffic calming measures shall apply to the removal of traffic calming measures. See Request, Petition, Evaluation, and Ballot policies. REQUEST INITIATED BY THE CITY: 1. The desire for a traffic calming measure may be deemed necessary, appropriate, or desired by the City. 2. If the scenario occurs where the City initiates the request for traffic calming measures, the standard policies may be modified at the discretion of the City. 3. A neighborhood meeting shall occur between the City and property owners located within the impact area. The purpose of this meeting is to discuss the preliminary concept plan and receive feedback. 4. The City shall give notice of the meeting at least thirty (30) days prior to the meeting, and directly notify property owners located within the impact area. 5. For a city-initiated request, the City shall be responsible for funding the construction of a traffic calming project. 6. For a city-initiated request, the City shall be responsible for funding the removal of a traffic calming project. 11

14 6.0 RESPONSIBILITY The City shall bear the following responsibilities: 1. Preparation of traffic calming documents (Request, Petition, Ballot, Removal Request) 2. Distribution of the Traffic Calming Petition to the citizen representative 3. Distribution of the Traffic Calming Ballot to property owners within the impact area 4. Data collection, as deemed necessary by the City, for the consideration of traffic calming measures 5. Engineering evaluation 6. Preparation of a concept plan 7. Notification of the neighborhood meeting to property owners within the impact area 8. Design and construction of traffic calming measures 9. Removal of traffic calming measures 10. Maintenance of traffic calming measures (if applicable); restricted to the component whose primary function is to operate as a traffic calming measure The citizen representative and/or property owners within the impact area shall bear the following responsibilities and costs: 1. Distribution of the Traffic Calming Petition to property owners within the impact area 2. Maintenance of traffic calming measures (if applicable); restricted to the component whose primary function is to operate as decoration/landscaping/aesthetics 12

15 7.0 COST The City shall be responsible for the following costs: 1. Construction of traffic calming measures, if the City initiates the process 2. Removal of traffic calming measures, if the City initiates the process The citizen representative and/or property owners within the impact area shall be responsible for the following costs: 1. An Application Fee may be required by the City in conjunction with the submittal of a Traffic Calming Petition, for either installation or removal. 2. Construction of traffic calming measures, if the property owners within the impact area initiate the process 3. Removal of traffic calming measures, if the property owners within the impact area initiate the process 13

16 8.0 TOOLBOX This toolbox of traffic calming measures provides guidance and information to the City and citizens. It provides the description, advantages, and disadvantages of various traffic calming measures. There are three (3) primary types of traffic calming: passive, vertical, and horizontal. Measures that are not considered traffic calming are also described and explain the reasons for not being appropriate traffic calming measures. Smaller and less expensive alternatives to the vertical and horizontal measures are also described, and can be applied either instead of or in conjunction with the physical measures. Traffic management techniques, which are not considered traffic calming, are also briefly described with advantages and disadvantages. Below is a summary of the traffic calming measures included in this toolbox: Passive - Education - Dynamic Speed Display Sign - Targeted Speed Limit Enforcement - Speed Legend - Radar Trailer Placement Vertical - Speed Hump - Raised Crosswalk - Speed Cushion - Raised Intersection - Speed Table - Textured Pavement Horizontal - Neighborhood Traffic Circle - Intersection Bulbout - Roundabout - Choker - Chicane - Center Island Median - Lateral Shift Not Traffic Calming - STOP Sign - Rumble Strip - CHILDREN AT PLAY Sign - Speed Bump - SPEED LIMIT Sign Alternatives - Additional Signs - Raised Pavement Marker - Lane Striping - Delineator - Optical Speed Bar - High Visibility Crosswalk Traffic Management - Full Closure - Median Barrier - Half Closure - Forced Turn Island - Diagonal Diverter 14

17 8.1 PASSIVE TRAFFIC CALMING MEASURES Passive traffic calming measures do not require construction of physical modifications to the roadway. Passive traffic calming often results in lower cost and prevents constructing a more-permanent change to the roadway. Physical (vertical and horizontal) traffic calming measures will be considered by the City when either the passive measures have not alleviated the neighborhood concerns or the City determines the need for their installation. Passive traffic calming measures include education, targeted speed limit enforcement, radar trailer placement, dynamic speed display signs, and speed legends. Education Activities that change people s perceptions and help alter driver behavior are most preferred. Meetings and workshops with neighbors and the City can help implement and direct traffic calming applications. Most traffic problems are a result of human behavior. Through outreach programs and neighborhood watch programs, residents can play a big part in spreading the information. Advantages: Flexible in the duration of meetings, workshops, etc. Inexpensive compared to other alternatives Disadvantages: Difficult to measure the effectiveness May take time to be effective Potential challenge in generating citizen participation 15

18 Targeted Speed Limit Enforcement The City can provide targeted speed limit enforcement in response to citizen concerns. Targeted speed limit enforcement may be considered for evaluating the level of speed reduction possible with more permanent measures. Targeted enforcement can also be used in conjunction with new physical traffic calming measures to help drivers become aware of the new traffic calming restrictions. This measure typically only provides a temporary benefit, since speed limit enforcement typically is not performed on a regular, on-going basis. Advantages: Inexpensive if used temporarily Does not require time for design Does not slow emergency vehicles Effective in reducing speeds in a short timeframe Disadvantages: Effectiveness may be temporary Expensive to maintain a continued program of enforcement 16

19 Radar Trailer Placement A radar trailer is a temporary device that measures an approaching vehicle s speed and displays it next to the posted speed limit. This can serve as a reminder to the driver of both the vehicle s speed and the posted speed limit. In order to be most effective, the placement of the trailer should be in the clear view of the oncoming driver s line of sight. These trailers can be easily placed on a roadway for a limited amount of time and then relocated to another roadway, allowing a single trailer to be effective in many locations. Like targeted speed limit enforcement, the placement of a radar trailer provides a temporary benefit for reduction of vehicular speeds; speeds tend to increase after the trailer is moved. Advantages: Inexpensive if used temporarily (less expensive if purchased) Does not require time for design Does not slow emergency vehicles Effective in reducing speeds in a short timeframe Disadvantages: Effectiveness may be temporary Aesthetics are not pleasing Only effective for one direction of travel Subject to vandalism 17

20 Dynamic Speed Display Sign A dynamic speed display sign performs the same function as a radar trailer, but is meant to be installed as a permanent device. Real-time speeds are relayed to drivers and flash when vehicle speeds exceed the posted speed limit. Dynamic speed display signs are typically mounted on or near the posted speed limit signs. While intended for permanent use, these can also be established as mobile units. Advantages: Inexpensive Does not require time for design Does not slow emergency vehicles Effective in reducing speeds in a short timeframe Disadvantages: Requires power source Only effective for one direction of travel Long-term effectiveness is uncertain Subject to vandalism 18

21 Speed Legend Speed legends are numerals painted on the roadway, indicating the current speed limit in miles per hour. They are usually placed near speed limit signposts. Speed legends can be useful in further communicating the posted speed limit, and can be placed at major entry points into a residential area. Advantages: Inexpensive Helps reinforce the posted speed limit Does not require time for design Does not slow emergency vehicles Disadvantages: Has not been shown to significantly reduce travel speeds 19

22 8.2 VERTICAL TRAFFIC CALMING MEASURES Vertical traffic calming measures provide an obstruction that vehicles are able to travel over. The change in pavement height (and sometimes pavement materials) can cause discomfort to the occupants of vehicles that are exceeding the design speed of the traffic calming measure. It should be noted that most vertical traffic calming measures are not preferred along roadways that are emergency vehicle routes or transit routes. To reduce the chances of potential liability issues, vertical traffic calming measures should be signed and marked in accordance with reference material provided by the Institute of Transportation Engineers (ITE) and the Manual on Uniform Traffic Control Devices (MUTCD). Vertical traffic calming measures typically perform better when they are installed in a series, as opposed to a single isolated measure. The deceleration and acceleration of a vehicle, while negotiating a series of vertical traffic calming measures, is dependent on the number and spacing of the installations. ITE states that the typical spacing for speed humps is 300 to 600 feet; however, this spacing guidance can be applied to all vertical traffic calming measures. The implementation of vertical traffic calming measures can result in some traffic diverting onto parallel streets. This essentially moves the cut-through problem instead of solving it. Consideration should be placed on the concept of improving the neighborhood (not just improving the street). Vertical traffic calming measures include speed humps, speed cushions, speed tables, raised crosswalks, raised intersections, and textured pavements. 20

23 Speed Hump Speed humps are raised areas of pavement (or other textured materials) in the street that are rounded and wave-shaped. Speed humps typically measure between three (3) and four (4) inches in height and twelve (12) feet in length. The height and length of the speed hump determines how fast it can be navigated without causing discomfort to the driver. Discomfort increases as the speed of the vehicle traveling over the hump increases. Advantages: Low Cost Effective in reducing vehicle speed Disadvantages: Increases response time for emergency vehicles Increases noise and air pollution in neighborhood May be damaged by snow plows 21

24 Speed Cushion Speed cushions are narrower speed humps that are typically installed in the center of each travel lane. Speed cushions typically are six (6) feet in width. Speed cushions typically range in length between seven (7) and ten (10) feet. Passenger vehicles will traverse the speed cushions in the same manner as a speed hump. However, emergency vehicles are able to straddle the speed cushions due to their wider wheel track. Thus, response times for emergency vehicles are not increased as much (if at all). Advantages: Less expensive than speed humps Effective in reducing vehicle speed Does not impact emergency vehicle response time as much as speed humps Disadvantages: Increases noise and air pollution in neighborhood Passenger vehicles with larger axle widths may be able to straddle the speed cushions May be damaged by snow plows 22

25 Speed Table Speed tables are flat-topped speed humps. Speed tables typically measure between three (3) and four (4) inches in height and 22 feet in length, with the flat portion being ten (10) feet in length. Speed tables are typically long enough for the entire wheelbase of a passenger car to rest on the flat top. Their long flat fields give speed tables higher design speeds than speed humps. The brick or other textured materials are usually used on the flat top to improve the appearance of speed tables, draw attention to them, reduce speed, and may enhance safety. Like speed humps, discomfort increases as the speed of the vehicle traveling over the hump increases. Speed tables are good for locations where low speeds are desired but a somewhat smooth ride is needed for larger vehicles. Advantages: Quicker response time for emergency vehicles than speed humps Effective in reducing vehicle speed, but not as well as speed humps Addition of brick or textured materials can improve aesthetics Disadvantages: More expensive than speed humps Increases response time for emergency vehicles Increases noise and air pollution in neighborhood May be damaged by snow plows 23

26 Raised Crosswalk Raised crosswalks have a similar shape to a speed table, but the flat top contains a striped pedestrian crosswalk. These measures should be elevated to a height that matches the adjacent sidewalk, such that the raised crosswalk is flush with the curb or top of sidewalk elevation at each end. There are not presently many curbs or sidewalks within the City. However, raised crosswalks must be installed with the appropriate sidewalk transitions on both sides in order to be compliant with the Americans with Disabilities Act of Advantages: Provides a more visible pedestrian crossing Quicker response time for emergency vehicles than speed humps Effective in reducing vehicle speed, but not as well as speed humps Addition of brick or textured materials can improve aesthetics Disadvantages: More expensive than speed humps Increases response time for emergency vehicles Increases noise and air pollution in neighborhood May be damaged by snow plows NOTE: Lack of sidewalk infrastructure may result in a raised crosswalk not being applicable in the City. Raised crosswalks can be constructed without the presence of sidewalks, as long as there are ADA-compliant pedestrian landing areas with detectable warning strips on both ends of the raised crosswalk. 24

27 Raised Intersection Raised intersections can be used as a traffic calming measure while also alerting drivers to the potential for pedestrians or vehicles at an intersection. The physical attributes are similar to a speed table in that each intersection approach elevates to a height of three (3) inches over a length of six (6) feet. The flat top, also similar to a speed table, is provided throughout the entire intersection. Advantages: Provides a more visible pedestrian crossing Provides traffic calming along two roads Quicker response time for emergency vehicles than speed humps Effective in reducing vehicle speed, but not as well as speed humps Addition of brick or textured materials can improve aesthetics Disadvantages: Very expensive compared to speed humps and speed tables More expensive than speed humps Increases response time for emergency vehicles Increases noise and air pollution in neighborhood Could create drainage impacts May be damaged by snow plows May be damaged by snow plows 25

28 Textured Pavement Textured pavement and stamped asphalt can be used alone as a traffic calming measure or in combination with other physical measures. Drivers typically slow down when crossing textured pavement due to vibration created by the pavement surface. However, this also creates considerable noise that may be a disadvantage for neighbors. Advantages: Pleasing visual aesthetics Disadvantages: Noise pollution Higher cost Not as effective in reducing speeds 26

29 8.3 HORIZONTAL TRAFFIC CALMING MEASURES Horizontal traffic calming measures incorporate raised islands and curb extensions to prevent vehicles from traveling in a straight line at excessive speeds. Vehicles either slow down while maneuvering around the horizontal obstacle, or slow down due to the physical perception of a narrower roadway. To reduce the chances of potential liability issues, horizontal traffic calming measures should be signed and marked in accordance with reference material provided by the Institute of Transportation Engineers (ITE) and the Manual on Uniform Traffic Control Devices (MUTCD). The implementation of horizontal traffic calming measures can result in some traffic diverting onto parallel streets. This essentially moves the problem instead of solving the problem. Consideration should be placed on the concept of improving the neighborhood (not just improving the street). Horizontal traffic calming measures include neighborhood traffic circles, roundabouts, chicanes, lateral 27

30 Neighborhood Traffic Circle Neighborhood traffic circles are raised islands placed in intersections, forcing traffic to circulate around the raised island. The traffic circle is typically circular in shape and can include landscaping within the raised island. The raised island in the center of the intersection typically measures between 16 and 24 feet in diameter. Neighborhood traffic circles can be controlled by YIELD signs on all approaches, STOP signs on all approaches, or a combination of free-flow conditions along the major street and STOP signs along the minor street. Traffic circles prevent drivers from speeding through intersections by impeding the through movement. Neighborhood traffic circles are most effective when there is vertical planting material in the center. This adds to its visibility to the driver and provides aesthetics to the neighborhood. Advantages: Effective in reducing vehicle speed Can reduce severity of motor vehicle collisions Opportunity for landscaping and improved aesthetics Disadvantages: Difficult for left-turning emergency vehicles Possible need for right-of-way, depending on size of raised island Increased cost/labor for maintenance of landscaping 28

31 Roundabout Unlike traffic circles, roundabouts are larger and typically require additional right-of-way. The central island diameter of a single-lane roundabout can measure between 55 and 110 feet. Roundabouts require raised splitter islands to channel approaching traffic to the right. Roundabouts are found primarily on arterial and collector streets, often substituting for intersections that are controlled by traffic signals or all-way stop signs. More information on roundabouts can be found in Roundabouts: An Informational Guide prepared by the Federal Highway Administration (FHWA). Advantages: Moderates traffic speed on an arterial, collector, or local road Enhanced safety compared to a traffic signal Less expensive to operate than a traffic signal Opportunity for landscaping and improved aesthetics Disadvantages: May require major reconstruction of an existing intersection Increases pedestrian distance from one crosswalk to the next Difficult for visually impaired pedestrian to navigate Increased cost for maintenance of landscaping 29

32 Chicane Chicanes are curb extensions that alternate from one side of the street to the other, creating S-shaped travel patterns. Raised landscaped islands or delineators are usually provided at both ends of a chicane in order to enhance the drivers awareness of the need for a lateral shift. Along a section of roadway that contains a chicane, off-street parallel parking may be restricted along property frontages due to curb and gutter. Advantages: Discourages high speeds by forcing horizontal deflection Easily negotiable by emergency vehicles Opportunity for landscaping and improved aesthetics Disadvantages: Must be designed carefully to discourage drivers from deviating out of the appropriate lane Curb realignment and landscaping can be expensive, especially if there are drainage issues Increased cost for maintenance of landscaping 30

33 Lateral Shift Lateral shifts can be described as one half of a chicane. Curb extensions or pavement markings are provided on otherwise straight streets that cause travel lanes to bend one way and then bend back the other way to the original direction of travel. With the appropriate degree of deflection, lateral shifts are one of the few measures that have been used on collectors or even arterials. When high traffic volumes and high posted speed limits prevent the use of other traffic calming measures, lateral shifts can be considered. Advantages: Can accommodate higher traffic volumes than many other traffic calming measures Discourages high speeds by forcing horizontal deflection Easily negotiable by emergency vehicles Opportunity for landscaping and improved aesthetics Disadvantages: Must be designed carefully to discourage drivers from deviating out of the appropriate lane Curb realignment and landscaping can be expensive (pavement markings are less expensive) Increased cost for maintenance of landscaping 31

34 Intersection Bulbout A bulbout can also be called a neckdown, intersection narrowing, or curb extension. These curb extensions reduce the roadway width at intersections, thereby reducing speeds when drivers experience the physical perception of a narrow roadway. The curb extensions may consist of concrete curbing, a line of bollards, or any other obstruction deemed appropriate. When using bollards or any other obstruction, the spacing of these objects should be between four (4) and six (6) feet such that the opening is smaller than the width of a vehicle. Intersection treatments reduce vehicle travel speeds by tightening the curb radii. Bulbouts improve pedestrian safety by providing a refuge and shortening the crossing distance. Intersection treatments can be retrofitted into an existing intersection without modifying the existing drainage, or they can be designed to provide additional sidewalk width for increased pedestrian use or street furniture. The effects are increased pedestrian comfort and safety at the intersection. Advantages: Encourages a safer pedestrian environment by providing a shorter crossing distance Through and left-turn movements are easily negotiable by large vehicles Prevents parking too close to intersections Opportunity for landscaping and improved aesthetics Disadvantages: Effectiveness is limited by the absence of vertical deflection Difficult for right-turning emergency vehicles Increased cost for maintenance of landscaping May require bicyclists to briefly merge with vehicular traffic 32

35 Choker Chokers are curb extensions at mid-block locations, whereas bulbouts are at intersection locations. Chokers reduce the roadway width by widening the sidewalk or planting strip. The presence of curb extensions reduces speeds when drivers experience the physical perception of a narrow roadway. The curb extensions may consist of concrete curbing, a line of bollards, or any other obstruction deemed appropriate. When using bollards or any other obstruction, the spacing of these objects should be between four (4) and six (6) feet such that the opening is smaller than the width of a vehicle. If chokers are marked/striped as crosswalks, they are also called safe crosses. Chokers cause the roadway cross section to be narrower than the normal cross section. Advantages: Easily negotiable by emergency vehicles If designed well, can have a positive aesthetic value Opportunity for landscaping and improved aesthetics Disadvantages: Effectiveness is limited by the absence of vertical deflection May require bicyclists to briefly merge with vehicular traffic Increased cost for maintenance of landscaping 33

36 Center Island Median Center island medians are raised islands located along the centerline of a street that narrow the travel lanes at that location. The presence of a median, resulting in a smaller roadway width, reduces speeds when drivers experience the physical perception of a narrow roadway. The medians are often landscaped to provide visual amenity; they can also contain curb extensions that consist of concrete curbing, a line of bollards, or any other obstruction deemed appropriate. When using bollards or any other obstruction, the spacing of these objects should be between four (4) and six (6) feet such that the opening is smaller than the width of a vehicle. The median island can act as a gateway when placed at the entrance to a neighborhood. A median island of adequate width can also be referred to as a pedestrian refuge if located at a crosswalk and the median is accommodating for pedestrians. Advantages: If designed well, can have a positive aesthetic value Opportunity for landscaping and improved aesthetics Disadvantages: Effectiveness is limited by the absence of vertical deflection May interrupt driveway access to adjacent properties Increased cost for maintenance of landscaping 34

37 8.4 NOT TRAFFIC CALMING MEASURES Measures that are not considered to achieve traffic calming include STOP signs, CHILDREN AT PLAY signs, SPEED LIMIT signs, rumble strips, and speed bumps. STOP Sign Studies show that unjustified STOP signs reduce speed near the signs, but increase speeds along the roadway immediately after the signs. This is caused by motorists making up for lost time. Inappropriate STOP signs also increase air pollution, waste fuel, and create more traffic noise. When confronted with unreasonable and unnecessary restrictions (such as inappropriate STOP signs), motorists are more likely to violate them and develop contempt for all traffic signs. Studies have also shown that there are a high number of intentional moving violations when STOP signs are installed as speed breakers. The Manual on Uniform Traffic Control Devices (MUTCD) provides guidance and warrants for placement of a STOP sign in Section 2B. Placement of STOP signs should not be considered as a means to help calm traffic in a neighborhood unless the MUTCD criteria have been satisfied. In summary, STOP signs are not considered appropriate traffic calming measures. The installation of inappropriate STOP signs can result in an increase in speeds, accidents, and pollution. (Source: Will STOP Signs Slow Traffic on Our Streets? by Metro Nashville Public Works) 35

38 CHILDREN AT PLAY Sign Studies have shown that many signs in residential areas, which are installed to warn people of normal conditions, fail to improve safety. Warning signs can be effective tools if used sparingly and only to warn motorists of uncommon hazards that are not apparent to drivers. CHILDREN AT PLAY signs can give parents a false sense of security since drivers often disregard these signs. The Manual on Uniform Traffic Control Devices (MUTCD) rejects these signs because they openly suggest that playing in the street is acceptable. Since children live on nearly every residential block, CHILDREN AT PLAY signs would need to be placed on every roadway. Residential blocks with no signs might imply that no children live there, so it is acceptable to exceed the posted speed limit. In summary, CHILDREN AT PLAY signs are generally disregarded by motorists and give parents a false sense of security. (Source: Will CHILDREN AT PLAY Signs Slow Traffic on Our Streets? by Metro Nashville Public Works) 36

39 SPEED LIMIT Sign The posted speed limits for roadways are typically established based upon recognized engineering criteria related to the roadway design. For this reason, additional signage and/or adjusting the posted speed limit of a roadway are not considered to be traffic calming measures. These requests can be submitted to the City, but not as traffic calming measures. 37

40 Rumble Strip These measures are raised pavement sections that can be closely spaced along a roadway at regular intervals. Rumble strips are a road safety feature used to caution inattentive motorists of potential danger. As the motorist travels over the rumble strips, the vehicle experiences both noise and vibration to alert the motorist. They are typically installed along freeways and higher speed roadways to alert motorists that may begin to veer from the travel lane to the shoulder. Their purpose is to reduce the number of vehicles that depart the roadway; this is a common example of rumble strips used to enhance safety. Rumble strips can also be installed across the travel lane itself when unusual conditions exist ahead. They can be installed along the travel lanes of a higher speed roadway that contains an isolated all-way stop controlled intersection. A motorist may grow accustomed to traveling at a certain speed and otherwise may not expect to stop; the purpose of the rumble strip is to alert the driver. This is a common example of rumble strips to alert motorists of a condition that is unusual to a specific roadway. Rumble strips should not be used as traffic calming measures. These measures become less effective over time as the motorists grow accustomed to them. Rumble strips also increase noise levels for nearby residents and commonly require additional maintenance. 38

41 Speed Bump These measures should not be confused with speed humps. Speed bumps are vertical obstructions often found in privately-owned parking lots (shopping centers, schools, churches, parks, etc). Speed bumps typically measure between three (3) and four (4) inches in height and twelve (12) inches in length, and are often designed for a design speed that is much lower than a typical posted speed limit along a public roadway. In contrast, a speed hump is typically twelve (12) feet in length. Traffic calming measures should be designed and implemented with the purpose that vehicles will be able to comfortably travel at the posted speed limit. In contrast, speed bumps require vehicles to travel much slower to attain a comfortable travel speed. The necessary braking and slow speeds can create a safety hazard, possibly causing rear-end collisions. In summary, speed bumps should not be installed on public roads and are not considered to be a traffic calming measure. 39

42 8.5 ALTERNATIVES TO TRAFFIC CALMING MEASURES Additional Signs Signs are an effective tool for advising drivers of the numerous situations encountered on roadways. For example, residential roadways should not act as cut-through routes for trucks and heavy vehicles. If the amount of cut-through traffic is deemed unacceptable, NO TRUCKS signs can be installed to regulate the number of heavy vehicles that travel along the residential roadway. Lane Striping Lane striping can be used to create dedicated bicycle lanes, parking lanes, or pavement edge lines. Pavement markings can be implemented to narrow the vehicular travel lanes, giving the perception of a higher speed to encourage drivers to reduce their speed. Lane striping typically has a relatively low cost for design and construction. However, the reduction in speed has not been conclusively demonstrated based on past evidence. The increase in the maintenance required may offset the benefits derived from the installation of new lane striping. Optical Speed Bar Optical speed bars are a series of pavement markings spaced at decreasing distances perpendicular to the pavement edge lines and centerlines. These markings have been used in construction zones to provide drivers with the impression of increased speed. Lane striping typically has a relatively low cost for design and construction. However, although they are initially effective, the speed reduction diminishes over time. 40

43 Raised Pavement Marker (RPM) RPMs are reflectors which are installed on the roadway to help drivers visually identify the centerline, lane lines and pavement edge lines on roadways during inclement weather and nighttime hours. RPMs can also be arranged in a rectangular array across the thru lanes of a roadway to create a rumble strip. These rumble strips can be effective in reducing travel speeds, but also considerably increase the roadway noise. As a consequence of the noise created by RPM rumble strips, they are usually only placed in locations with a very low density of residential structures. Delineators Delineators are similar to RPMs except the reflectors are placed on a vertical plastic break away pole along the roadway edge to further define a centerline or pavement edge line of a roadway. Delineators help to add a vertical element to the pavement and are often used with other physical traffic calming measures to improve their visibility and effectiveness. Delineators usually do not require a large expenditure for design and can help in reducing the driver speeds when used to delineate physical devices. The cost for delineators, as well as possible replacement and maintenance costs, can cause this measure to be relatively expensive. Motorists and citizens may not consider delineators to be visually attractive, especially as they begin to experience wear and tear. High Visibility Crosswalk High visibility crosswalks can use pavement markings and colorless RPMs to enhance visibility. The pavement markings are typically solid white in color, eight (8) feet long, and twelve (12) inches wide. Drivers tend to be more aware of the high visibility crosswalks and usually slow down when they are approached. However, due to the higher cost, this measure should be restricted to locations that have both high vehicular volumes and pedestrian volumes. 41

44 9.0 TRAFFIC MANAGEMENT Diversion devices use a combination of raised islands and curb extensions to preclude particular vehicle movements at an intersection. These measures are considered to be traffic management, not traffic calming. Full Closure Full street closures are barriers placed across a street to close the street completely to through traffic. Sidewalks or bicycle paths typically remain open. The barriers may consist of landscaped islands, walls, gates, side-by-side bollards, or any other obstructions that leave an opening smaller than the width of a passenger car. Advantages: Able to maintain pedestrian and bicycle access Reduces traffic volumes on that street Opportunity for landscaping and improved aesthetics Disadvantages: Requires the City to enact an ordinance (possible 90-day process) Will increase traffic volumes along adjacent streets Causes longer travel time and distance for local residents and emergency vehicles May be expensive Increased cost for maintenance of landscaping Half Closure Half street closures are barriers that block travel in one direction for a short distance on otherwise two-way streets. Half closures are the most common volume control measure after full street closures. Half closures are often used in sets to make travel through a grid network of neighborhood streets circuitous rather than direct, with the intent being to reduce traffic volume in the neighborhood. The through movement should remain possible, but less attractive than alternative routes. Advantages: Able to maintain pedestrian and bicycle access Removes specific through traffic Opportunity for landscaping and improved aesthetics Disadvantages: Requires the City to enact an ordinance (possible 90-day process) Causes longer travel time and distance for local residents and emergency vehicles Drivers may disobey the half closure and proceed the wrong way through the measure May be expensive Increased cost for maintenance of landscaping 42

45 Diagonal Diverter Diagonal diverters are barriers placed diagonally across an intersection, blocking through movement. Like half closures, diagonal diverters are usually staggered to create circuitous routes through neighborhoods. Advantages: Able to maintain full pedestrian and bicycle access Removes specific through traffic Disadvantages: Requires the City to enact an ordinance (possible 90-day process) Causes longer travel time and distance for local residents and emergency vehicles May be expensive May require construction of corner curbs Median Barrier Median barriers are raised islands that are located along the centerline of a street and continue through an intersection. This blocks the through movement for vehicles at a cross street. Advantages: Can improve safety at an intersection of a local street and a major street by prohibiting dangerous turning movements Can reduce traffic volumes on a cut-through route that crosses a major street Disadvantages: Requires available street width on the major street Limits turns to and from the side street for local residents and emergency vehicles Forced Turn Island Forced turn islands are raised islands that block certain movements on approaches to an intersection Advantages: Can improve safety at an intersection of a local street and a major street by prohibiting dangerous turning movements Reduces traffic volumes Disadvantages: If designed improperly, drivers can maneuver around the island to make an illegal movement May simply divert a traffic problem to a different street 43

46 10.0 CONCEPTUAL DRAWINGS The following conceptual drawings of the traffic calming measures presented in this handbook are provided for informational purposes only. These conceptual drawings should not be considered a final design for any physical traffic calming measure. The following conceptual drawings are included: Bulbout (Intersection Treatment) Bulbout (Midblock Treatment) Center Island Narrowing Chicane Choker Raised Intersection Roundabout Speed Cushion Speed Hump Speed Table Traffic Circle 44

47 Sign Description OM = Object Marker Bulbout (Intersection Treatment) (Intersection Treatment) Sidewalk Planting/Mow Strip Crosswalk lines optional per MUTCD Wheelchair Ramps OM (Minimum 20') (8') typ. 45 OM 45

48 (Midblock Treatment) Bulbout (Midblock Treatment) NO PARKING 8 20 NO PARKING 30 The bulb-out drawing shown is for a 30 foot wide street. If a street is wider, the bulb would be deeper; each bulb shown is seven feet deep. The width between bulbs should be 16 feet, which allows cars to pass in opposite directions at slow speeds. The bulb would restrict parking for approximately 20 feet (one car length for parking purposes) in order for the bulb to be visible, allow wider vehicles to pull to the right and allow an opposing vehicle to pass. It may be possible to plant a tree in each bulb. 46

49 Sign Description R4-7 Keep Right Center Island Narrowing Center Island Narrowing Parking Prohibited 20' min. Edge line R=2' R4-7 6' Raised Pavement Marking (typ.) R4-7 Center line markings Taper length per MUTCD 8:1 min. (typ.) 11' 10' R=250' Existing curb 47

50 Chicane Optional pavement markers along centerline taper Sign Descriptions OM = Object Marker 8' min. extension (typ.) Existing curb 1'-2' drainage channel (typ.) OM 20' min. OM 24' Edge line OM 24' 45 from curbline (typ.) Center line markings Taper length per MUTCD 8:1 min. (typ.) Parking Prohibited 48

51 Choker CHOKER Parking Prohibited 30 (typ.) Existing curbline 45 (typ.) OM Direction of traffic Direction of traffic Center line markings Taper length per MUTCD 8:1 min. (typ.) 16' - typ. Pavement marker 20' - typ. R=4' OM Edge line Sign Descriptions 8' min. extension 36' - typ. 1'-2' drainage channel OM = Object Marker 49