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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