Lower speed limits save lives in London

Casualties drop 42%

Steve Hawley, Jan 06, 10.

The introduction of 20 mph urban speed limits in London has reduced the city’s traffic casualties by almost 42 percent, according to an article published in the British Medical Journal and cited in How We Drive.

The reduction in casualties was largest among children. How We Drive states, “[this] brings up the point that it’s not merely children’s risk-taking behavior responsible for their deaths as pedestrians, [but] that addressing driver’s behavior can make a difference.” Over the same time period, casualties on adjacent streets dropped eight percent, which How We Drive says could be part of a “carry-over effect.”

The article notes:

The reductions are impressive and seem beyond what might be explained by some other factor, such as a reduction in pedestrian volumes over that same time period (although other factors, like the presence of enforcement cameras, need to be kept in mind).

Not only were the speed limits reduced to 20 miles per hour, but many of the streets were also designed to be “self-enforcing” - that is, the design elements themselves encourage drivers to slow down. In fact, the study suggests that the average speed on self-enforcing roads is about 17 mph, a drop of 9 mph.

In the US, a recent study said that the road fatality rate increased when Congress abolished the national 55 mph speed limit in 1995. According to that study, the higher speed limits caused an additional 1,250 deaths per year.

Full paper: Effect of 20 mph traffic speed zones on road injuries in London, 1986-2006