Wiki Wednesday: Getting Streets in Shape With Road Diets

This morning Sarah wrote about the excessive width of many American roads, which makes speeding all too tempting for drivers. So I’m going to bookend my day with this StreetsWiki entry on road diets — 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 from Walkable Communities.
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.

  • mike

    Road diets are a great way to quickly improve a street, esp for cyclists and pedestrians. For the same cost of a typical sidewalk bulb out, you can re-stripe a mile of street.

    San Francisco has done 30 of these types of projects, with many more to come. I haven’t yet heard of another city in N America (or anywhere, for that matter) that has done more than SF.

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