Does Your City Make Its Roads Look Big?
Former NJ-DOT-er Gary Toth (now with the project for Public Spaces) recently visited the Netherlands, a country that not so long ago had a worse traffic safety record than the U.S., but which now has a far superior one. There are a number of explanations, but in an interesting post (which echoes some material in Traffic), he singles out differing national approaches to the “forgiving road” concept:
Forgiving Highways is a concept that designs roads to “forgive” mistakes made on the road. It seeks to smoothly redirect the vehicles that leave roads, and allow wide enough clear zones to bring vehicles to controlled stops if and when they leave the roads. Breakaway supports, burying the end of guardrail, clearing the roadside of unneeded obstacles, and flattening and rounding slopes and ditch sections became standard design as part of the concept.
The idea that Forgiving Highways (wider and straighter) would reduce crashes on non-freeways took root during the 1966 National Highway Safety hearings. Leading the way was a nationally revered expert on safety: Kenneth Stonex, who during his career at General Motors, oversaw much of the research that created the basis for the Interstate Highway safety standards. Justifiably marveling in the remarkable safety record of the Interstates, Stonex and others sought to apply the Interstate principles to the rest of our roads. “What we must do is to operate the 90% or more of our surface streets just as we do our freeways… [converting] the surface highway and street network to freeway road and roadside conditions,” Stonex testified. It sounded logical at the time… and a great political solution, because the responsibility for fixing the problem once again fell on government, not the individual. We dove deep into the Forgiving Highway philosophy and still have not come up for air.
The Dutch also believed in technology and Forgiving Highways. However, they began to notice that while this worked on the high speed freeways and the low speed residential areas, they still had a problem in their “built up” areas. Recognizing that it is in these areas that they have the biggest conflicts between the purpose of roads for moving people and the value of roads in providing for exchange and access, they began to commit themselves to a different approach. They began designing roads in built up areas that induced motorists to operate their vehicles in ways and at speeds that were appropriate for passage through urbanized areas. The Dutch came to understand that the post-World War II world wide approach to making roads wider, straighter and faster simply doesn’t work on local and commercial roads in urbanized areas.
In the US, application of the Forgiving Highways approach in urban areas did accomplish its mission when vehicles did leave the road. However, as an unintended consequence, vehicular speeds go up. Drivers responded to their environment. Put them on a stretch of road that is wider, flatter, and straighter and they drove faster. While okay on controlled access freeways where there are no adjacent land uses or pedestrians, and where sight distances are near infinite, curves are flat and opposing roadways are separated by wide medians or center barriers, higher speeds caused problems in built up areas. Yet we were so caught up in the paradigm that we never stopped to check to see if we were getting the desired result.
This entry was posted on Wednesday, August 12th, 2009 at 7:19 am and is filed under Cities, Traffic Engineering, Traffic safety. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.