On average, vehicles seriously injure or kill someone in New York every two hours; last year, 173 pedestrians were killed. Last week Gov. Andrew M. Cuomo signed a bill allowing New York City to enact a citywide default speed limit of 25 miles per hour as part of its “Vision Zero” campaign to reduce traffic deaths to nil.
When the speed at which a car strikes a pedestrian rises a mere 10 m.p.h. — to 40 m.p.h. from 30 — the chance of the pedestrian’s dying rises to 85 percent from 45. The real question is not absolute speed but appropriate speed.
There are two surefire ways to reduce speed: the speed bump which costs little and is effective in a blunt, limited way. The other, though still relatively rare in the United States, is ubiquitous elsewhere in the developed world: the speed camera.
• Unlike most traffic enforcement, cameras work because they are visible and predictable.
• Install them, and give drivers warning, and speeds will drop.
• Random enforcement provides a very weak feedback signal — when a strong signal is needed to curb habitual behavior
• Driving fast without being caught or crashing — determines “how your brain decides whether to remember a habit for the future.”
• Speed cameras have been shown to reduce crash and fatality rates.
• A majority of people support speed cameras when they are used in school zones, on roads with a history of crashes or where many drivers violate the speed limit.
• The use of cameras does raise legitimate issues about privacy, transparency and accuracy, but similar concerns exist with any form of enforcement.
In any case, enforcement — whether by cameras or cops — cannot deliver “Vision Zero.” To alter driver behavior on speeding, a city like New York will need more than a catchy slogan, a technical fix or ramped-up enforcement. Enter “psychological traffic calming.”
This approach relies on the suggestive power of context: Drivers tend to go at a speed that feels appropriate for the road they are on. For instance, does your street have a center dividing line? If so, add a few m.p.h. to the average traffic speed. Is it one-way? Add some. Does it have well-marked bike lanes? Cut a few m.p.h. Trees on the side? Drop some.
The effect of psychological traffic calming seems contagious and painless. Drivers can be nudged out of their worst instincts.