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Traffic Calming

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Project Background

The Town works with homeowners associations and community groups where there are no homeowners associations to design traffic-slowing devices where property owners agree to pay for them. Traffic calming measures are meant only as speed reduction devices in residential neighborhoods where traditional police enforcement is not consistently available. You may fill out a request form to mail, fax or e-mail.

A pilot study in 1999 evaluated devices to reduce speeding and cut-through traffic in neighborhoods. It determined that speed humps, raised pedestrian crosswalks and lane narrowing are effective countermeasures.

Project Scope

The process of requesting a traffic-slowing devices is summarized below.

The Town offers technical support however those requesting traffic calming devices are responsible for most of the work. The process can take six months to a year, depending on how often petition organizers revise their traffic calming plan to obtain neighborhood support. See the traffic calming policy and procedure for more information

Traffic Calming Device Alternatives

Traffic calming devices are designed for use to reduce vehicular speed and to enhance the livability of streets throughout communities and neighborhoods for non-motorists. This is an effort to promote safe transportation facilities for motorists, cyclists and pedestrian. In doing so, the Town of Cary has summarized various traffic calming devices and their impact for possible installation within the Town. The types of devices can be separated into three categories. Those categories are passive devices, horizontal deflecting devices and vertical deflecting devices.

1. Passive Devices

Passive traffic calming measures are designed to mitigate potential speeding issues by providing non-invasive techniques to calm traffic. Passive measures include education methods, police enforcement and parked cars on a street.

  • Education methods/Police Enforcement
    Information is sent to communities to inform then on the dangers of speeding. Periodic radar enforcement is also conducted. A speed sentry unit is used to collect speed and volume data while displaying a motorists speed in an effort to educate the driver that their speed might be inappropriate. The speed sentry might be useful in raising driver awareness of their travel speed.
  • Parked Cars On Street
    Parked cars on neighborhood streets can act as horizontal deflecting devices that narrows the width of the street. This type of action can give drivers the feeling that the lane width between opposing vehicles is narrow and thus traveling at a slower speed is necessary.

2. Horizontal Deflecting Devices

  • Traffic Circle
    A traffic circle is an elevated area in the middle of an intersection that allows the counter-clockwise flow of traffic for low-speed operations.
      Potential Impacts
      • Effective in reducing speeds
      • Decreases intersection related crashes
      • Right of way issues based on width of circle
      • Emergency vehicles can easily maneuver
      • Turning radius for larger vehicles (30 feet or greater)
      • Landscaping the center island can visually enhance the street
  • Median/Raised Island
    A median/raised island is an elevated area in the middle of a street that narrows opposing travel lanes in order to slow traffic. These types of devices are very useful in narrowing wide streets with pavement widths of 30 feet or greater. Lane widths are narrowed to a minimum of 10 feet for traffic calming purposes.
      Potential Impacts
      • Effective in reducing speeds
      • Constraining design to accommodate parking on the street
      • Reduces the street crossing width for pedestrians
      • Emergency vehicles can easily maneuver
      • Landscaping the median/raised island can visually enhance the street
  • Choker/Neckdown
    A choker is a physical constriction built along the curbside of a street to narrow a roadway. The choker extends the curb while widening the planting strip of a street. These types of devices work well in combination with speed humps and raised crosswalks. The design of the choker will limit lane widths to a minimum of 10 feet.
      Potential Impacts
      • Effective in reducing speeds when used in combination with other devices
      • Constraining design to accommodate parking on the street
      • Reduces the street crossing width for pedestrians
      • Emergency vehicles can easily maneuver when used as a stand alone measure
      • Landscaping the extended area can visually enhance the street.

3. Vertical Deflecting Devices

  • Speed Hump/Speed Table
    Speed humps are devices installed on residential streets and commercial parking lots for the purpose of reducing motor vehicle speeds. In Cary, speed humps are constructed with asphalt materials and are 22 feet in length with a maximum height of 3.0 inches. The Town installs two types of speed humps: parabolic and flat top. The design of the parabolic speed hump contains a 22 feet continuous run of asphalt that is parabolic shaped (semi-circle). The parabolic speed hump is designed for use in commercial areas.

    The design of the flat top speed hump contains two, six feet tapered sections with a 10 feet flat section in the middle. Since constructing the 10 feet flat section at a 3.0 inch height is difficult, typically a tolerance of 0.5 inches is given. The flat top speed hump is designed for use on residential streets. Spacing between speed humps range between 300-500 feet. When properly spaced, average speeds between speed humps range between 20 to 25 mph.

      Potential Impacts
      • Effective in reducing speeds (25 mph or less)
      • Increased response times for emergency vehicles (0-10 seconds)
      • Noise concerns due to deflection characteristics
      • Increased speeding between humps when not spaced properly
      • Studies show that speed humps do not impact home resale values
      • Only appropriate on residential streets, not on collectors and roads with higher classifications
  • Raised Crosswalk
    Raised crosswalks are devices installed on residential streets to reduce speeds while providing a marked crossing area for pedestrians. The design of the raised crosswalk is similar to the flat top speed hump. The 10 feet flat section is striped with thermoplastic pavement markings to designate a pedestrian crossing.
      Potential Impacts
      • Effective in reducing speeds (25 mph or less)
      • Increased response times for emergency vehicles
      • Noise concerns due to deflection characteristics
      • Only appropriate on residential streets, not on collectors and roads with higher classifications
      • Current and Pending Projects - Coming Soon

Reporting Speeders

To report speeding in the neighborhood, call the Cary Police Department’s traffic safety line at (919) 319-4521. Please specify the location and times when the problem is greatest.

Contact

Julie Green - Traffic Engineer
Transportation & Facilities Department
Town of Cary
(919) 462-3945
julie.green@townofcary.org

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