Cul-de-sacs Kill!

Update: 11/20/09

The slides are now online.

Original Post: 11/5/09

I’m attending the Congress for New Urbanism Transportation Summit here in Portland this week (where I’ve had the opportunity to meet several other transportation bloggers!).

For me the highlight presentation on opening day on Wednesday was about the safety affects of different street network types.

The study was based on looking at all cities in California with population of 40,000 or greater. The surprising finding was that cities built before 1950 are safer (in terms of both serious injuries and fatalities for all classes of users: auto drivers/passengers, cyclists and pedestrians) than cities built after 1950.

The differences appears to be in the type of street network. Compact street grids seem to be safer, compared to the arterial-collector-local street ‘tree’ style of street network popular in post-war development.

This explains a lot here in Portland, particularly the difference in traffic safety between inner neighborhoods new parts of Portland near or east of 82nd Avenue (illustrated by an example from current news).

I’ll post a link to the research report when it’s available online.

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