YY's bike shed: Traffic calming works, and it's cheap

I wrote a letter to the city asking to make traffic calming the default

I went down a rabbit hole on traffic calming and wrote two pages: Traffic calming works and Traffic calming is cheap. Based on these, I also wrote a letter to Charlottesville’s mayor, council, and transportation staff with three main requests: a citywide daylighting program, a Safe Streets Ordinance that makes calming the minimum standard for residential streets, and a standing traffic-calming program. If you live in Charlottesville too, feel free to borrow any of it. Also please let me know if you find any issues.

Some key points:

• Changing the number on a sign does almost nothing: England’s signed-only 20 mph limits changed speeds by 0.38 mph. Physical calming in British 20 mph zones cut them by 9.3 mph.
• In London’s calmed zones, casualties fell about 42%, and deaths and serious injuries to children fell roughly by half. Across London, Toronto, New York, and Oakland, measured cuts to children’s pedestrian injuries cluster around 40–50%.
• Hoboken, NJ—a real American city of 60,000—has not lost a single person to traffic in nine years. Its signature tools: plastic posts, paint, and curb extensions.
• The prices are so cheap compared to other road-related cost: a daylighting post costs $40 in hardware, a speed hump about $3,000 installed. Speed humps along an entire mile cost about $40,000—roughly 2–3% of what repaving that same mile costs.
• NHTSA prices one traffic death at $11.3 million—five thousand speed humps. If five thousand humps prevent a single death over their lifetime, the whole program has paid for itself.
• One year of crashes in Charlottesville (pop. 45,000) costs $23–$30 million in economic terms alone; the measured crash reductions from calming would repay humps on fifty miles of streets in under a year.
• The carbon cut from the mode shift comes along for free—plausibly more tons per year than the climate programs cities actually budget.

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