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Traffic Circles

Traffic circles are different than typical roundabouts. In a traffic circle, side streets are under a STOP condition and the main road has the right-of-way.

In addition to providing a center-island green space with yield signs and low speeds, traffic circles are safer than your average four-way intersections. They can also be less confusing once you get used to them, since every motor vehicle is turning in a counterclockwise direction. They are typically used in residential neighborhoods to slow traffic speeds and reduce accidents, but are not usually designed to accommodate larger vehicles.

Who has the right of way? 

If a vehicle is already in the traffic circle, they have the right of way.

How do you drive in a traffic circle?

When you get to the traffic circle and see that it’s clear of other vehicles, bicyclists, and pedestrians, it’s time to enter the circle. Turn right. Traffic circles are basically one-way streets. A left turn into a traffic circle could end in a head-on collision.

Traffic Circle Pattern

 

Project Background

The Town works with homeowner associations and community groups where there are no homeowner 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 have an area evaluated.

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.
  • Requests are evaluated on a first-come, first-served basis.
  • If a location is approved for study, there will be extensive data collection.
  • A summary of results is provided for review.
  • Town staff meets with neighborhood representatives to discuss concerns and design alternatives.
  • Police and fire department representative reviews for any emergency response issues.
  • A traffic calming concept plan is developed.
  • Neighborhood petition requires 70 percent support.
  • Town Council approval is also required.
  • The neighborhood group must provide 25 percent of total construction costs before design occurs.

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 Criteria and Guidelines for more information.

Traffic Calming Device Alternatives

Traffic calming devices are designed to reduce vehicular speed and to enhance the livability of streets throughout communities and neighborhoods for nonmotorists. This is an effort to promote safe transportation facilities for motorists, cyclists, and pedestrians.

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. 

Educational 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 narrow the width of the street. This gives drivers the feeling that the lane width between opposing vehicles is narrower, resulting in slower speeds.

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 to slow traffic. These types of devices are 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 curb 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 standalone 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 and are 22 feet long with a maximum height of three inches. The Town installs two types of speed humps: parabolic and flat top. The design of the parabolic speed hump contains a 22-foot 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-foot, tapered sections with a 10-foot flat section in the middle. Since constructing the flat section at a three-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 and 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-foot 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

      Reporting Speeders

      To report speeding in your 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

      David Spencer, PE
      Traffic Engineering Supervisor
      Transportation & Facilities Department
      Town of Cary
      (919) 462-3833
      david.spencer@townofcary.org

      Rob Myers
      Traffic Engineer
      Transportation & Facilities Department
      Town of Cary
      (919) 380-4236
      rob.myers@townofcary.org