Traffic Calming

This partial closure allows cyclists and pedestrians to pass but requires automobiles to use higher volume streets.

Twenty-five years ago, Dutch city planners began designing neighborhood streets in which it was practically impossible to drive a car at greater than walking pace; indeed, motor vehicle traffic was so unobtrusive that even though the streets had no raised sidewalks, people could walk, ride bikes, play, and even meet and converse with their neighbors without fear. The Dutch called these streets "woonerven" or "living yards". A woonerf usually featured a brick or paving block surface with speed humps, twists and turns, carefully managed parking, and a variety of other features designed to slow traffic down and discourage it from entering in the first place.

Gradually, the concept of woonerven spread to streets other than purely residential, and to other countries. The Germans adapted the idea and applied the phrase "traffic calming" to this kind of street design. They also began to develop 30 km/hr streets and zones that were not quite as radically altered as woonerven, but still slowed traffic down with physical changes such as chicanes, speed humps, speed tables, raised intersections, and mini-roundabouts or traffic circles.

In the late 1990's traffic calming began to become more widespread in United States communities. The Institute of Transportation Engineers and the Federal Highway Administration recently teamed up to develop a detailed state of the practice report on traffic calming in the US that documents the experience of 20 communities with a variety of traffic calming devices. In addition, they collected numerous resources on traffic calming, and developed a training course on the subject.

The Federal Highway Administration inaugurated a new web site dedicated to all the known and/or electronically publicized transportation programs and studies that pertain to traffic calming. Additional FHWA/ITE web sites can be found at FHWA - Traffic Calming.

One issue that the FHWA/ITE report deals with only briefly is whether traffic calming benefits bicycling. Some bicyclists are concerned that the traditional techniques used to slow traffic down have a negative impact on them:

  • Street narrowings that tend to slow motorists can mean that motorists drive closer to bicyclists when passing them or try to "beat" the cyclist to the narrower section of the road.
  • Speed humps and other devices that change the level of the roadway may be uncomfortable and inconvenient for bicyclists. Another problem with speed humps is that drivers may try to swerve around the edges to avoid the full impact of the hump, which encourages them to swerve into where the bicyclist is riding along the curb. This is a real problem with speed humps and bicycles.

In the ITE report Traffic Calming: State of the Practice, author Reid Ewing quotes from Boulder, Colorado bicyclists who opposed some traffic calming projects for these reasons.

Throughout the rest of Europe, however, there has been widespread acceptance that traffic calming can benefit bicyclists. Clarke and Dornfeld (FHWA, 1994) concluded in a report written as part of the National Bicycling and Walking Study that "the experience from Europe clearly shows that bicycle use has been encouraged by traffic calming".

  1. Well designed and implemented traffic calming measures can have a number of beneficial impacts for bicyclists and pedestrians. The reduced vehicle speeds associated with such projects can reduce both the severity and incidence of motor vehicle/ bicycle crashes and can make bicyclists feel more comfortable in traffic.
  2. In certain situations, traffic calming techniques may be used to reduce the number of motor vehicles traveling along particular streets, and can increase the number of bicyclists.
  3. Traffic calming techniques can be used to provide better roadway conditions for bicyclists by better defining the space available to each mode, by improving intersection design for nonmotorized users and by giving greater priority to their movement.

David Davies, presenting at the 1999 Velo City conference in Graz, Austria, wrote that "traffic calming should benefit bicyclists in so far as it reduces motor vehicle speeds. Indeed, Hass Klau (1991) found that it was a more effective way of encouraging cycling than the creation of cycle routes."

In the US, design information that addresses the needs of bicyclists in the development of traffic calming measures can be found at in several communities, including the City of Cambridge, Mass.