Neighborhood Traffic Management Program A6 Study Area Plan

Transcription

1 Neighborhood Traffic Management Program A6 Study Area Plan Azalea Trace, Barclay Hills, Brassfield, Cape Cottages, Colony Woods, Cornerstone, Fairlawn, Hunters Crossing, Hunting Ridge, McClelland Estates, McClelland Townhomes, McClelland Woods and Yester Oaks Prepared by the City of Wilmington Development Services Department May 2008

2 City of Wilmington, North Carolina Development Services Department 305 Chestnut Street, Floor 4 Post Office Box 1810 Wilmington, NC Kaye Graybeal, Director of Development Services Ron Satterfield, Planning Manager Mike Kozlosky, Senior Transportation Planner Joshuah Mello, Associate Transportation Planner Anthony Prinz, Associate Transportation Planner William McDow, Staff Engineer May 2008 Page 2 of 24

3 Table of Contents Boundary of A6 Study Area History of Neighborhood Traffic Management Program..4 Neighborhood Traffic Management Program Objectives Interim and Long-range Solutions...6 Characteristics of the A6 Study Area.7 Traffic Data for the A6 Study Area...8 Analysis of Geometric Improvements and Crashes for the A6 Study Area Existing Traffic Calming Devices in the A6 study area...10 Public Input...10 Interim Improvements...11 Long-Range Improvements...12 Appendix A: Public Meeting Minutes...16 Appendix B: Common Traffic Calming Devices...19 List of Figures and Tables Figure 1- Boundary of A6 Study Area....4 Figure 2- Completed Study Areas Figure 3- Existing Roadways...7 Table 1- Volume and Crash Data 8 Figure 4- Speed Limits 11 Figure 5- Pavement Markings and Bicycle Lanes.. 12 Figure 6- Impeller Locations...13 Figure 7- Choker Locations 13 Figure 8- Roundabout Location.14 Figure 9- Multi-use Path Location.14 Figure 10- Traffic Signal Location.15 Figure 11- Collector Street and Roundabout Location...15 May 2008 Page 3 of 24

4 Boundary of A6 Study Area The study area for this report includes the Azalea Trace, Barclay Hills, Brassfield, Cape Cottages, Colony Woods, Cornerstone, Fairlawn, Hunters Crossing, Hunting Ridge, McClelland Estates, McClelland Townhomes, McClelland Woods and Yester Oaks neighborhoods. Figure 1: Boundary of A6 Study Area History of the Neighborhood Traffic Management Program (NTMP) Efforts to alter driver behavior in residential neighborhoods by the city have a long-standing history as indicated by records from the 1970s when selected streets in the Glen Meade/South Oleander neighborhoods were made one-way so as to discourage cut-through traffic. In 1986, consultants recommended the installation of multi-way stops at selected intersections in five neighborhoods (including the Glen Meade/South Oleander area) as an effort to reduce speeds and cut-through traffic. Three years later the devices were evaluated by staff to determine their effectiveness. Data showed that the full compliance rate in Wilmington (15%) at the unwarranted multi-way stops was significantly lower than the national rate (50%) and speeds had increased above pre-installation levels. As a result, city council resolved in 1989 that unwarranted multi-way stops would no longer be installed in the city. May 2008 Page 4 of 24

5 Before the evaluation of the multi-way stops was completed, participants at the Forest Hills neighborhood public meeting requested that the city remove the multi-way stops in Forest Hills and reduce the speed limit on Forest Hills and Colonial drives to 25 miles per hour (mph). Their chief complaint was that drivers were not stopping at the multi-way stop intersections. Traffic speeds continued to exceed the 25 mph posted limit. Another effort was made to reduce speeds and traffic volumes in the Forest Hills neighborhood by installing three speed humps on a trial basis in the vicinity of Forest Hills school in Evaluation data taken eleven months after the installations showed that speeds were reduced slightly, but remained higher than the posted speed limit of 25 mph. There were no significant changes in traffic volumes. Public perception was that speed humps were effective, which resulted in an increase in the number of requests for the devices. Between 1994 and 2004 the city installed more than 130 speed humps on neighborhood streets. Following a national trend and input from emergency management entities, the city discontinued the use of these devices due to the adverse effect on emergency vehicle response times and maintenance, The Neighborhood Traffic Management Program (NTMP) was created in The program placed greater emphasis on street networks within a defined area so as to provide solutions that benefited the neighborhood as a whole, as opposed to focusing on one particular street. Staff researched other geometric design features, such as chokers, chicanes, and mini-circles as means of traffic calming. A public involvement process was instituted, whereby public meetings are hosted by city staff prior to the development of a plan and after the completion of a draft plan. Both interim and long-range traffic calming solutions were defined based on data and staff observations, as well as resident involvement. Since its inception staff has conducted studies in 18 areas and held 36 meetings with over 1,600 participants. Neighborhood Traffic Management Program Objectives Create safe and attractive streets Minimize cut-through traffic Reduce crash frequency & severity Increase safety for non-motorized street users Reduce the need for police enforcement Promote pedestrian, cycle and transit use Incorporate the preferences of residents Increase quality of life for residents Help in reducing the negative effects of motor vehicles on the environment May 2008 Page 5 of 24

6 Figure 2: Completed Study Areas Interim and Long-range Solutions Interim solutions are designed to be implemented by city staff within a twelve-month period. Longrange solutions are much more complex and costly. These solutions usually require engineering design, city capital improvement program funding, and construction by a contractor. Typical Interim Solutions White edgeline pavement markings Double yellow centerline pavement markings Marked crosswalks near pedestrian facilities and schools Regulatory signs within neighborhood study areas Street trees in some neighborhoods Reduction of speed limit to twenty-five miles per hour on local streets Bicycle improvements Typical Long-Range Solutions Choker islands (Center choker or Bulb-outs) Roundabouts (mini-roundabouts and full-roundabouts) Impellers Intersection realignment Sidewalk installation May 2008 Page 6 of 24

7 Characteristics of the A6 Study Area The study area includes a combination of single-family and multi-family homes, as well as apartment complexes and a mix of businesses. The predominant housing type for the Barclay Hills and Fairlawn neighborhoods is single-family homes, while townhouses, apartment complexes and large condominium buildings are found in the other areas. North Kerr Avenue, classified functionally as a minor arterial, is maintained by the North Carolina Department of Transportation. This roadway divides the A6 study area into two smaller sections. State Transportation Improvement Program (STIP) project U-3338 will widen North and South Kerr Avenue to a four-lane divided facility, from Martin Luther King, Jr. Parkway to Randall Parkway. The city has requested that NCDOT incorporate sidewalks and bike lanes into the design for this project. Figure 3: Existing Roadways Most of the city-maintained streets in the study area function as local streets. The exceptions are Birchwood Drive, Columb Drive, Hunters Trail, Lennon Drive, New Centre Drive, Ringo Drive and Sunglow Drive. Due to existing traffic volumes, connectivity with local and arterial streets and future development potential, these streets function as collector streets. Many of the streets in the study area are characterized by long, straight segments with few or no traffic calming devices. There are existing speed humps on McClelland Drive between North Kerr Avenue and Saint Rosea Drive; the May 2008 Page 7 of 24

8 posted speed limit on this segment is 25 miles per hour (mph). The speed limit on the other streets in the area is 35 mph. Traffic Data for the A6 Study Area Table 1 represents an analysis of the volume and crash data of public roadways with the study area. Three streets had 85 th percentile speeds that were at least 5 mph higher than the posted 35 mph speed limit. Barclay Hills Drive, between Princess Place and Tiffany Drives, had the highest 85 th -percentile speed Table 1: Volume and Crash Data Street Between Vehicles per day 85 th Percentile Speed (MPH)* *The 85 th -percentile speed is the speed at which 85% of the vehicles travel at or below **From January 1, 2007 to March 10, 2008 Reported Crashes** Angle Crashes Barclay Hills Dr Princess Pl Dr & Tiffany Dr 2, Barclay Hills Dr Tiffany Dr & Fairlawn Dr 1, Estate Dr Dewitt Rd & Fairlawn Dr Fairlawn Dr Barclay Hills Dr & N Kerr Ave 1, Birchwood Dr Princess Pl Dr & N Kerr Ave McClelland Dr St Rosea Dr & N Kerr Ave 1, McClelland Dr N Kerr Ave & Cobblestone Dr Cobblestone Dr Market St & McClelland Dr 2, Clover Rd McClelland Dr & Fairlawn Dr Dewitt Rd Estate Dr & Gleason Rd Gleason Rd McClelland Dr & Fairlawn Dr Sunglow Dr Kerr Ave & Tabor Ct 1, Sunglow Dr Indica Ct & Tabor Ct 1, Sagedale Dr N Kerr Avenue & end Lennon Dr Gingerwood Dr & Ringo Dr 3, Hunters Tr Lennon Dr & Lennon Dr 1, Hunters Tr Ringo Dr & Lennon Dr 3, Ringo Dr Columb Dr & Lennon Dr 3, Ringo Dr Lennon Dr & Hunters Tr 4, recorded within the study area, at 44.1 mph. The 85 th -percentile speed of traffic on Barclay Hills Drive was 25% higher than the 35 mph speed limit. Fairlawn Drive had an 85 th -percentile speed of 40.7 mph, which was 16% higher than the 35 mph speed limit. Fairlawn Drive is used as a shortcut between North Kerr Avenue to Princess Place Drive. Hunters Trail, between Lennon Drive and Lennon Drive had an 85 th -percentile speed of 40.9 mph, which is 16.8 % higher than the posted speed. May 2008 Page 8 of 24

9 Crash data for the area was studied from January 1, 2007 to March 10, Six streets had four or more vehicle crashes since January 1, These streets were Barclay Hills Drive, Lennon Drive, McClelland Drive, Cobblestone Drive, Sagedale Drive and Hunters Trail. Hunters Trail between Ringo Drive and Lennon Drive had the higher number of vehicle crashes, with nine total crashes and seven angle crashes. Stop sign violations at the intersection of Hunters Trail and Lennon Drive was the predominate contributor to the angle crashes on this street. Lennon Drive between Gingerwood Drive and Ringo Drive had the second highest number of vehicle crashes, with seven total crashes and five angle crashes. Stop sign violations also contributed to the number of angle crashes on this street. Analysis of Geometric Improvements and Crashes in the A6 Study Area A crash analysis of the intersections within the A6 study area revealed problems at the following intersections: Hunters Trail at Lennon Drive: angle crashes and stop sign violations Ringo Drive at Lennon Drive: angle crashes and stop sign violations McClelland Drive at Cobblestone Drive: sideswipe and rear-end with parked vehicles Sagedale Drive at N Kerr Avenue and: angle crashes involving vehicles attempting left turns Angle crashes documented at the Lennon Drive and Hunters Trail intersection represented over 50% of the crashes reported for these two streets. Due to the left-turn lanes on Lennon Drive, multi-way stop signs are not recommended for the intersection of Lennon and Ringo Drives. Other geometric improvements to this intersection, such as the installation of a roundabout, may improve its safety. Additional crashes were examined on roadway segments within the study area. Along Lennon Drive, narrow street width appeared to contribute to the number of vehicles involved in on-street collisions. The subject vehicles tended to be un-occupied, parked vehicles that were near entrances to parking lots and apartments in the area. Speed and alcohol consumption was listed as a contributing factor in some of the incidents, however, many of the collisions were coded as hit and run accidents and no further information was available. Accidents along Cobblestone Drive and McClelland Drive followed a similar pattern to those on Lennon Drive. Rear-ends with parked vehicles and hit and run collisions were the most frequent types of accidents. Four of the McClelland Drive crashes listed the location of the reporting vehicles as parked in the travel lane. One accident report stated that the vehicle that struck the parked vehicle disregarded the pavement markings. May 2008 Page 9 of 24

10 Hunters Trail had three on-street collisions reported between January 1, 2007 and March 10, All three crashes involved parked vehicles. Speed and alcohol was a factor in one of the crashes, while driver inattention was cited in another. Existing Traffic Calming Devices in the A6 Study Area There are existing speed humps on McClelland Drive between North Kerr Avenue and Saint Rosea Drive. Residents of McClelland Drive petitioned the city for the installation of the speed humps to address speeding and cut-through traffic. After a traffic study was completed on the street, speed humps were installed in Public Input To encourage citizen participation, staff mailed informational cards to each residence fronting a local, public street in the study area. The first meeting for the study area was held at Rachel Freeman Elementary School on January 29, Staff briefed the attendees about the NTMP process and enlisted input so as to identify transportation concerns within the study area. Participant comments were recorded by staff and used to develop interim and long-range solutions to the identified neighborhood traffic issues. A second meeting was held on March 25, 2008 at Rachel Freeman Elementary School where staff presented the proposed solutions to the attendees. Suggested changes or additional recommendations by participants were documented. The outcome of the meetings is a strategic plan for managing traffic issues in the interim and long term for the neighborhoods. May 2008 Page 10 of 24

11 Interim Improvements Speed Limits: A reduced speed limit of 25 miles per hour is recommended for the local streets within the study area. Collector streets, including Birchwood Drive, Columb Drive, Hunters Trail, Lennon Drive, New Centre Drive, Figure 4: Speed Limits Ringo Drive and Sunglow Drive, will remain at 35 miles per hour. Figure 4 indicates the proposed speed limits on the roadways within the study area. This will preserve access and mobility for the entire area, as these collector streets serve a function above and beyond access to adjacent properties. These streets connect local streets to arterials and provide access to large tracts of undeveloped land. Pavement Markings: Two ten-foot-wide travel lanes will be marked on Barclay Hills Drive, Cobblestone Drive, Hunters Trail and Greentree Road. This will create the illusion of a narrower roadway and potentially reduce travel speeds, while deterring vehicles from straddling the pavement edge. Existing turn lanes will be removed on McClelland Drive; the street will be re-striped to add parking lanes. May 2008 Page 11 of 24

12 Bicycle Lanes: Two four-foot-wide bicycle lanes will be striped on Cobblestone Drive and Greentree Road where sufficient pavement width exists. A Share the Road sign will be installed on Cobblestone Drive southbound, just before the existing median. Figure 5: Pavement Markings and Bicycle Lanes Long-Range Improvements Impellers: Impellers are used as a means of controlling vehicle speed near T-intersections. While intersection chokers or neck-downs slow traffic using a narrowed roadway segment, impellers use a horizontal shift to reduce vehicle speeds. May 2008 Page 12 of 24

13 Figure 6: Impeller locations Chokers: Chokers are curb extensions at midblock locations that narrow a street by widening the sidewalk or planting strip. Two-lane chokers leave the street cross section with two lanes that are narrower than the normal cross section. Figure 7: Choker locations May 2008 Page 13 of 24

14 Roundabouts: Figure 8: Roundabout location Roundabouts require traffic to circulate counterclockwise around a center island. Unlike traffic circles, roundabouts are used on higher volume streets to allocate right-of-way between competing movements. A full-sized roundabout is proposed at the intersection of Lennon and Ringo Drives to reduce the number of angle crashes at this intersection. Bicycle and Pedestrian Facilities: A multi-use path is proposed to connect Cobblestone Drive to the existing multi-use path along New Centre Drive. This will provide pedestrian and bicycle connectivity between different land uses. Sidewalks and four-foot bicycle lanes will be installed along North Kerr Avenue as part of the North Carolina Department of Transportation STIP project U Figure 9: Multi-use path location Miscellaneous Improvements: A traffic signal is proposed at the North Kerr Avenue and New Centre Drive intersection as part of the North Carolina Department of Transportation STIP project U-3338, which will widen North Kerr Avenue to a four-lane divided facility. An extension of Hunters Trail is proposed. As development occurs a roundabout is proposed where Hunters Trail presently terminates, utilizing the existing cul-de-sac pavement. May 2008 Page 14 of 24

15 Figure 10: Traffic signal location Figure 11: Collector street and roundabout locations May 2008 Page 15 of 24

16 Appendix A: Public Meeting Minutes January 29, 2008 Meeting Transportation Planning staff held the first of two public meetings with the residents of the A6 study area. Approximately 25 residents attended the meeting at the Rachel Freeman Elementary School on January 29, The focus of the meeting was resident s concerns regarding traffic along the local streets in the study area. City staff provided an overview of the Neighborhood Traffic program, explained traffic calming procedures, described transportation projects near the area, and reviewed traffic data and existing speed limits within the area. Sgt. Carl Strawn was present to address Wilmington Police Department (WPD) enforcement efforts along the local streets in the area and WPD resources to patrol the area. Residents discussed pedestrian safety concerns and expressed their desire for lower speed limits and traffic calming devices within their area. The following comments are a summary of resident s comments during this meeting: Speeding is a problem in the area, reduce speed limit to 25 mph on local streets Speeding on Hunters Trail is a major problem Drivers on Hunters Trail increase their travel speed after they cross Lennon Drive intersection Drivers on Hunters Trail pass cars that drive the speed limit It is difficult to turn left into your driveway on Hunters Trail due to unsafe passing by vehicles on this street Speeds on Barclay Hills Drive reach 40 to 50 mph Access to Princess Place Drive from Barclay Hills Drive is especially hard during peak hours Drivers on Barclay Hills Drive do not slow down for pedestrians walking on the street Drivers on Hunters Trail speed up once they reach Rolling Rd Pedestrians and cyclists are endangered by Hunters Trail traffic Add centerlines to Clover Rd and Hunters Trail Use enforcement fines to pay for street repairs Traffic volume and traffic noise are high on Hunters Trail Add centerlines on Fairlawn Drive to keep vehicles in their travel lanes Pavement markings on Barclay Hills Drive, Fairlawn Drive and Clover Rd would help pedestrians Clover Rd and Barclay Hills Drive need repairs to the pavement surface School buses on Fairlawn Drive and Barclay Hills Drive run off the side of the road when they meet along the street, due to the narrow width of the street Turning vehicles at Fairlawn Drive and North Kerr Avenue have caused pot holes and ruts at the edge of pavement WPD enforcement along Barclay Hills Drive should use the center section of the street, not the end of the street Sidewalks and walking paths are needed for Clover Rd Turn lanes, sidewalks and bike lanes are needed for North Kerr Avenue Drivers on North Kerr Avenue. use the center lane as a merge lane Repair McClelland Drive at Kerr Avenue, due to a divot within the pavement at this location Cobblestones Drive needs speed humps or other traffic calming devices May 2008 Page 16 of 24

17 Revisit new lane pattern at New Centre Drive and Market Street (add a second through lane to Target) Change timing for signal at Kerr and Market Street during peak hour traffic Add centerline and reduce speed limit to 25 mph on Sagedale Drive Vehicles exiting from Cobblestone Drive have a difficult time turning left High number of vehicles per day on Ringo Drive and Hunters Trail will make the proposed WAVE Transit bus station unsafe Lower speed limit to 25 mph in the study area Enforcement for 25 mph speed limit will be difficult Mini-bikes on Kornegay Avenue and North 30 th Street are a problem Increase police patrols on Barclay Hills Drive after 6:00pm and during morning peak hours Check warrants for new signal at Princess Place Drive and Barclay Hills Drive Cobblestone Drive: vehicles illegally pass Check drainage on Clover Rd Three vehicles were totaled on Cobblestone Drive within the past few months Implement more traffic stops and insurance checks by the police on Barclay Hills Drive and Fairlawn Drive Add sound barriers along Martin Luther King, Jr. Pkwy and Market Street March 25, 2008 Meeting Transportation Planning staff held the second of two public meetings with the residents of the A6 study area. Approximately 15 residents attended the meeting at the Rachel Freeman Elementary School on March 25, During the meeting city staff presented a plan for traffic calming strategies developed to managing traffic issues over the short-term and long-term for these neighborhoods. The plan was developed in response to issues that were identified during the January 29, 2008 meeting. City staff provided an overview of the neighborhood plan and explained how it would be implemented through interim and long-range solutions. City staff explained traffic calming procedures, described transportation projects near the area, and listened to resident requests for additional traffic calming devices. Sgt. Carl Strawn was present to address Wilmington Police Department enforcement efforts along the local streets in the area. Residents approved the plan and requested modifications to the list of streets which will remain at 35 mph, and the addition of more traffic calming devices, in order to further enhance pedestrian safety concerns and lower speed limits within their area. The following comments are a summary of resident s comments during this meeting: Why is Cobblestone Drive shown as collector street? Response: It functions as collector street Cobblestone Drive and Barclay Hills Drive shown as 35 mph street, lower speed to 25 mph Why is Fairlawn Drive not shown as a collector street? Response: It will not future development in the future May 2008 Page 17 of 24

18 People will not change speed from Fairlawn to Barclay Hills; therefore both streets should have the same speed limit Mailboxes along Barclay Hills Drive are across the street and there are lots of elderly residents in the area, please lower speed to 25 mph. Response: Staff will re-evaluate Fairlawn Drive, Barclay Hills Drive and Cobblestone Drive Did staff work with NCDOT to develop Kerr Avenue widening plan? Response: Yes How will residents exit Fairlawn Drive after the median is added for the North Kerr Avenue widening project? Response: Fairlawn Drive is planned to be right-in and right-out only, residents will have to make a u-turn to go north on North Kerr Avenue Talk to NCDOT to change the plan for limiting left turns into and from Fairlawn Drive Birchwood Drive has no driveways or mailboxes on the street, it should be 35 mph Explain how pavement markings will work on Hunters Trail and Cobblestone Drive. Response: Staff explained how pavement markings would create 10ft travel lanes, bike lanes and parking areas Add a choker or impeller to Cobblestone Drive. Response: Staff will study the street for the additional traffic calming device Ditches on Clover Rd are too deep and do not drain properly. Response: Issue will be referred to the Stormwater Services Division May 2008 Page 18 of 24

19 Appendix B: Common Traffic Calming Devices Traffic calming measures can be separated into two groups based on the main impact intended. Volume control measures are primarily used to address cut-through traffic problems by blocking certain movements, thereby diverting traffic to streets better able to handle it. Speed control measures are primarily used to address speeding problems by changing vertical alignment, changing horizontal alignment, or narrowing the roadway. Typical traffic calming devices include chicanes, chokers, raised intersections, roundabouts, traffic circles, mini-circles and impellers. Chicanes Chicanes are also called deviations, serpentines, reversing curves, or twists (Photo courtesy of Calming State of the Practice) Chicanes are curb extensions that alternate from one side of the street to the other, forming s- shaped curves. Chicanes can also be created by alternating on-street parking, either diagonal or parallel, between one side of the street and the other. Each parking bay can be created either by restriping the roadway or by installing raised, landscaping islands at the ends of each parking bay. Uses: Chicanes are best used in locations where speeds are a problem but where noise associated with speed humps and related measures would be unacceptable. Advantages: Discourage high speeds by forcing horizontal deflection Easily negotiable by large vehicles (such as fire trucks) except under heavy traffic conditions Disadvantages: Must be designed carefully to discourage drivers from deviating out of the appropriate lane Curb realignment and landscaping can be costly, especially if there are drainage issues May require the elimination of some on-street parking May 2008 Page 19 of 24

20 Choker Chokers are also called pinch points, midblock narrowings, midblock yieldpoints, and constrictions (Left photo courtesy of Calming State of the Practice, right photo from Burnett Boulevard) Chokers are curb extensions at midblock locations that narrow a street by widening the sidewalk or planting strip. If marked as crosswalks, they are also known as safe crosses. Two-lane chokers leave the street cross section with two lanes that are narrower than the normal cross section. Onelane chokers narrow the width to allow travel in only one direction at a time, operating similarly to one-lane bridges. Uses: Chokers are best used in areas with substantial speed problems and no on-street parking shortage. Advantages: Easily negotiable by large vehicles (such as fire trucks) Can have positive aesthetic value, if designed well Reduce both speeds and volumes Disadvantages: Effect on vehicle speeds is limited by the absence of any vertical or horizontal deflection May require bicyclists to briefly merge with vehicular traffic May require the elimination of some on-street parking May 2008 Page 20 of 24

21 Raised Intersections Raised intersections are also called speed tables, raised junctions, intersection humps, or plateaus (Photo courtesy of Raised intersections are flat raised areas covering an entire intersection, with ramps on all approaches and often with brick or other textured materials on the flat section. They usually rise to the level of the sidewalk, or slightly below to provide a lip that is detectable by the visually impaired. By modifying the level of the intersection, the crosswalks are more readily perceived by motorists to be "pedestrian territory". Uses: Raised intersections are best used at intersections where there is substantial pedestrian activity, and in areas where other traffic calming measures would be unacceptable due to the elimination of scarce parking. Advantages: Improve safety for both pedestrians and vehicles Can have positive aesthetic value, if designed well Can calm two streets at once Disadvantages: Tend to be expensive, varying by materials used Impact to drainage needs to be considered Less effective in reducing speeds than speed humps or raised crosswalks May 2008 Page 21 of 24

22 Modern Roundabouts Roundabouts are also called traffic circles or rotaries. (Photo courtesy of Center for Transportation Research- Kansas State University) Modern roundabouts require traffic to circulate counterclockwise around a center island. Unlike traffic circles and rotaries, roundabouts provide horizontal deflection and a clearly-defined travel path. Uses: Locations with a history of accidents Intersections where queues need to be minimized Intersections with irregular approach geometry Providing inexpensive-to-operate traffic control as an alternative to a traffic signal Handling a high proportion of u-turns Locations with abundant right-of-way Advantages: Moderate traffic speeds on an arterial Aesthetically pleasing, if well designed Enhance safety compared to traffic signals Minimize queuing at the approaches to the intersection Less expensive to operate than traffic signals Disadvantages: May be difficult for large vehicles (such as fire trucks) to circumnavigate Must be designed so that the circulating lane does not encroach on the crosswalks May require the elimination of some on-street parking Must be maintained, either by the residents or by the municipality May 2008 Page 22 of 24

23 Mini-circles Mini-circles are also called neighborhood traffic circles or mini-roundabouts. (Photo of mini-circle at the intersection of Kornegay Street and Clammy Street) Mini-roundabouts require traffic to circulate counterclockwise around a center island. Unlike roundabouts, mini-circles are used on lower volume streets to allocate right-of-way between competing movements. Key design features are the offset distance (distance between projection of street curb and center island), lane width for circling the circle, the circle diameter, and height of mountable outer ring for large vehicles such as school buses and trash trucks. Geometric design is limited to one lane in each direction. Uses: Locations with a history of accidents Intersections with irregular approach geometry Locations with limited right-of-way Advantages: Require motorists to yield to motorists already in the intersection Require drivers to slow to a speed that allows them to comfortably maneuver around them Not as expensive as full roundabouts Used at intersections of local or collector streets No effect on access Aesthetically pleasing, if well designed Disadvantages: Not typically used at intersections with high volume of large trucks and buses turning left Approximate delay of between 5 to 8 seconds for fire trucks to drive around circle Large vehicles may need to turn left in front of the circle Can result in bicycle/auto conflicts at intersections because of narrowed travel lane May 2008 Page 23 of 24

24 Impeller Impeller Impellers are used as a means of controlling vehicle speed near T-intersections. While intersection chokers or neck-downs slow traffic using a narrowed roadway segment, impellers use a horizontal shift to reduce vehicle speeds. Impellers are used in the U.S, Australia and other countries to prevent accidents and wide right hand turn. Additionally, impellers prevent vehicles from rounding a turn or crossing into the path of vehicles approaching the stop controlled portion of an intersection. (Photo courtesy of Calming State of the Practice) Uses: Intersection treatment at t-intersections Off-set intersections with a history of accidents Intersections with limited right-of-way Areas where good sight distance is important Advantages: Decreases accidents within the intersection Lowers speed at the intersection Protects right turning vehicles Disadvantages: Possible loss of parking near the impeller Difficult to maneuver vehicles with trailers within the impeller May create a squeeze-point for cyclists if bike lanes are not installed Landscaping opportunities may be limited by size and type of impeller used May require curb realignment on narrow streets May be more expensive than chokers May 2008 Page 24 of 24