Traffic Calming Measures

As motor vehicle design has evolved, so has the need to separate traditional arterial traffic management from neighborhood traffic management. Traffic calming is a way to alter roadway design in order to mitigate the impacts of vehicle technology. Below is a list of calming devices developed around the world, as well as in the United States, each device performing a different function.

Traffic Circles

Typically 20 to 25 feet in diameter, traffic circles are normally placed within intersections. The size and shape of circles can vary as determined by the physical construction of the intersection and the desired result specific to the location. Circles can be planted with shrubs, or may have mountable curbs to facilitate emergency vehicles in response time.

Objectives: Better regulate uncontrolled intersections; create visual screen or break along line of roadway.

Application: Applied only at intersections; local access streets only; recommended for intersections where vehicle right-of-way may be uncertain.

Advantages: Reduces vehicle speeds at the device location; reduces collision points and severity when accidents occur.

Speed Bumps

The Watts Style Bump is 14 feet through the travelway, designed on a parabolic arc to affect speeds in a 25 MPH environment.

Objectives: Reduce vehicle speeds; enhance neighborhood livability.
Application: For use on local access streets; may be used in conjunction with other devices.

The (Seminole Style) Collector Bump is 22 feet through the travelway, designed for arterial volumes and speeds not exceeding 45 MPH. A flat ten foot center with six-foot parabolic ramps on each side allow speeds between 25 and 35 MPH.

Medians

Medians are generally center-street located and used to separate opposite lanes. They can take on many designs in order to address site-specific issues such as allowing free-flow in one direction while restricting flow in the other. Landscaping can be used to conform with neighborhood visual enhancement or business themes.

Objectives: Provide a visual cue of change in roadway environment.

Application: Medians may be used in conjunction with other traffic calming devices.