Wednesday, July 10, 2013

Taming the Urban Arterial – Trees!

One of the persistent causes of argument between local governments and state DOTs is….trees!  Towns love the idea of planting street trees in the medians of ugly urban arterials, as a way of at least putting some lipstick on these eyesores.  To state DOT traffic engineers, however, street trees are just another kind of “fixed object in the clear zone” – a source of crash danger for vehicles leaving their lanes.
Now, thanks to the Washington State DOT and the University of Washington, we have a longitudinal study over several years comparing actual crash data on urban arterials with different forms of medians (including medians with “small” trees) and similar control sections (report here).
The results?  Trees aren’t a problem! 
To oversimplify, almost any kind of median reduces crashes.  Whether or not there are trees in the median doesn’t seem to matter.

Kudos to WsDOT and U of W for a very good study that should have real practical effects in helping engineers and planners at both the local and state level “tame” those ugly urban arterials.

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