In the 12 years since London started charging people to drive downtown, traffic and pollution has fallen sharply. No surprise there. What is surprising though, is accidents have declined sharply as well. In other words, congestion pricing saves money---and, more importantly, lives.
A study by three economists at the University of Lancaster found traffic collisions have fallen 40 percent since between 2000 and 2010. That drop is an unintended but welcome benefit of a program that has reduced traffic, curbed emissions and raised more than $300 million every year to improve mass transit.
"The evidence suggests that the congestion charge helps in accomplishing the government objective of fundamentally changing behavior" of those headed into central London, the researchers write.
Since February 2003, motorists driving into central London on most weekdays have paid $17.40 for the privilege. Transport for London, that city's version of the DOT, reported a roughly 10 percent drop in traffic volume in the zone. A paper the Journal of Economic Perspectives published in 2006 showed that included a 34 percent drop in cars entering the area, and a 28 percent increase in cyclists. Nitrogen and carbon dioxide emissions dropped as well, but it’s unclear how much of that could be attributed to vehicles becoming increasingly efficient.
Reducing accidents wasn’t a goal, nor was it a given. One result of decreased congestion is higher average speed, so more accidents, particularly involving pedestrians or cyclists, wouldn’t be surprising. Until now, however, there has been little data to suggest what actually was happening. Transport for London estimated in 2008 it “had contributed to an additional reduction of between 40 and 70 collisions” per year, but didn’t put that finding in a larger context.
“It seemed surprising that there really wasn’t much research looking at its effect on motor vehicle fatalities [and] injuries,” says Colin Green, an economics professor and lead author of the new study, to be presented this month at the Royal Economic Society’s annual conference.
Using public data on collisions and government traffic flow data, correlated with the congestion zone using GIS and statistical software, Green and his co-authors compared accident rates in London and 20 other UK cities between 2000 and 2010. The result was clear: a 40 percent drop in accidents per vehicle mile driven---that’s the rate of crashes, not just the total---in the congestion zone. “There’s a big drop in flows, but there’s an even bigger drop in accidents,” Green says. “There’s just less cars to hit each other.”
What’s more, the charge is linked to a drop in accidents beyond the specified zone and during times---evenings, weekends and holidays---when the congestion charge is not levied. Green credits that to the scheme’s (intended) impact on human behavior. The government treats the congestion charge as a carrot and a stick: It uses the revenue to improve mass transit and cycling infrastructure to make those options more desirable, and punishes those who choose to drive.
London’s not the only city that has tried out congestion pricing: Singapore, Stockholm, and Milan all have similar plans in place. A recently proposed plan would have New York City try the same thing. There’s plenty of opposition from those who don’t like the idea of more government-imposed fees, but data like this, showing London’s plan has saved lives while reducing traffic and pollution, makes that argument a bit harder to make.
