Traffic Calming Basics
by Richard Untermann

An introduction to "traffic calming" -- with examples of several techniques for reducing traffic speed and improving the pedestrian environment.

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Traffic calming represents a decision to improve the pedestrian environment by reducing traffic speed and volume, without eliminating access for those living or doing business on the street and without preventing emergency vehicle access. Traffic calming can also help strengthen the fabric of neighborhoods by making streets less of a barrier.

How can we calm traffic? Let me first discuss some basic traffic calming approaches that do not involve modifying the street, and then turn to strategies that do entail street modifications. ... Physically altering the street has become an increasingly popular approach to reducing vehicle speeds. One way to do this is by narrowing short sections of streets from two to one lane. Called chicanes, the one lane portion requires one driver to wait while the other passes. Seattle has converted portions (up to 150 feet long) of two way streets to one way, using extended curbs to block wrong way access, and to shorten pedestrian street crossings.

Islands and medians placed in the roadway can also help slow traffic down, visually reinforcing the message that the road is not designed for high speeds. In addition, through landscaping and tree plantings, islands can create a more attractive street environment.

... My favorite street narrowing technique is widened sidewalks at intersections. Variously called bulb-outs, neck-downs, or safe-crosses, they include an enlarged sidewalk “bulb” that projects out into the street --

reducing the street width and, as a result, the pedestrian crossing distance. The bulb usually goes about 6 feet into the street, and is 20 to 30 feet long. Safe-crosses often include trees or landscaping, and benches; and also frequently serve as bus stop locations. They can be either single or double (i.e., with a bulb on each side of the street). ...

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