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
- Traffic Calming and ITE
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 motorists
may try to "beat" the cyclist to the narrower section of the road.
In the ITE report, author Reid Ewing quotes from Boulder, Colorado
bicyclists who opposed some traffic calming projects for these reasons.
Speed humps and other devices that change the level of the
roadway may be uncomfortable and inconvenient for bicyclists,
and abrupt changes in level may even have the potential to throw
Cyclists in the United Kingdom dealt with this issue in the
late 1980s. The
Cyclists Touring Club published a special report on cyclists
and traffic calming which was generally supportive but warned
of the dangers of poorly designed traffic calming techniques
that could indeed make life harder for bicyclists.
Throughout the rest of Europe, however, there was widespread acceptance
that traffic calming was a huge benefit to 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".
Summary: Traffic Calming, Auto Restricted Zones and Other Traffic
Management Techniques. Case Study #19, National Bicycling and Walking
A paper to the 1993 Velo City conference in Nottingham, England, described
how the application of a general 30 km/hr speed limit in the city
of Graz, Austria was considered an essential element of bicycle promotion.
Traffic crashes fell by 30 percent. Although crashes involving bicyclists
rose by 2 percent, there was no increase in the number of bicyclists
injured and a 40 percent decrease in the number of bicyclists seriously
injured. In addition, there was a presumption that levels of bicycling
had increased. And, bicyclists were the strongest supporters of the
30 km/hr measures, with 81 percent for the project.
- 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.
- 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.
- 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 the following websites: Oregon
DOT, and City
of Cambridge, Mass.