When were your neighbourhood streets designed?

An interesting, and counter-intuitive, correlation has been discovered by two urban geographers. The rate of fatalities in road accidents in cities in California depends on when the street grid was laid out. And, despite the belief that town planning has become better, the correlation is that older, more grid-like, layouts are safer. A possible reason is that grids make motorists stop and start more often, and so may drive more slowly. There's a popular account of this at:

It emphasizes the O.R. principle of determining what system one is trying to optimize. Town planners may have designed curving roads, with tree structure and cul-de-sac roads to reduce through traffic but "the system" extends to the environment of work, shopping and leisure as well as where people live.


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