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Wiki Wednesday: Getting Streets in Shape With Road Diets

This morning Sarah wrote about the excessive width of many American roads [1], which makes speeding all too tempting for drivers. So I'm going to bookend my day with this StreetsWiki entry on road diets [2] -- the practice of reducing the number of travel lanes -- from author Andy Hamilton:

toronto_road_diet.jpgPhoto: Dan Burden.
Road diets are anathema to traditional traffic engineering principles because they tend to reduce roadway capacity. However, in practice, road diets can cause vehicle speeds to readjust to a more optimal speed, increasing the throughput of vehicles per lane. For this reason, road diets sometimes reduce congestion, and generally always increase safety for all users of the roadway. Studies in Seattle found that road diets decreased the rate of crashes by 6%.

The need for road diets comes from the fact that multi-lane urban roads are built to handle large volumes of traffic during the morning and evening rush hours. Generally, during the other 22 hours of the day, the road is larger than necessary. This abundance of spare pavement encourages speeding, and places bicyclists and pedestrians at far higher risk than a typical two-lane road.

One of the references in this entry comes from Dan Burden and Peter Lagerwey's "Road Diets: Fixing the Big Roads," available as a PDF [3] from Walkable Communities [4]. It's a bit of an oldie but definitely a goodie if you're looking for more facts, figures, and stories about implementing road diets.