Monday, February 1, 2010

The Design of Everyday Roads

I have been thinking about the design of roads. For the most part, speed limits are set based on the safe speed to travel on the road (I'm sure there are limits that could be higher or should be lower, but the basic premise is that speeds are set for real reasons). The problem is that roads are not always designed to encourage people to drive those speeds. One of my favorite books is Donald Norman's The Design of Everyday Things. He talks about how the design of simple objects can either suggest to the user how the objects should be used (not by printed instructions but by the way the objects are made) or give the user bad information that makes the objects difficult to use (think about a corkscrew; it almost works itself because every part tells you what to do with it).

Roads are the same way. We know a lot about how to drive on a road by the way it is designed, but I submit that we don't know how fast to drive by the way the roads are designed. In my trip to work (if I don't take the highway), I drive on roads that are 25 m.p.h., 30 m.p.h., 35 m.p.h., and 40 m.p.h. The problem is that it is very difficult to tell the difference just by driving on the road. I'm not saying the speed limits are wrong; I'm assuming that they are correct. I'm saying that the design of the road should suggest the speed. For example, my accident took place on a road that is 30 m.p.h., but almost no one drives 30 m.p.h. (and the woman who lives near the accident scene says that accidents happen there regularly). Donald Norman might suggest that if everyone is trying to drive 40 or 45, then it's not the fault of the people but the design of the road. Why is it that the 30 m.p.h. roads are as wide if not wider than the 40 m.p.h. roads? Width is one tip that you can drive faster.

I've never met anyone who likes "traffic calming" (speed bumps, speed humps, traffic circles, narrow sections, etc.), but if the road is designed to make you think you can go fast, that might be the only solution.

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