Don’t Count on Mass Transit Improvements to Reduce Traffic Congestion

No traffic jams in Pyongyang. Because Pyongyang sucks.

Photo by Feng Li/Getty Images

Construction is beginning on a Bus Rapid Transit project in Alexandria, Va., that looks pretty cool. Unfortunately, as is often the case with transit projects, proponents are overselling the benefits to nonusers of the system: “officials hope the route will ease traffic along Route 1.”

Anything’s possible. But as transit advocates know, more highway construction tends not to reduce highway congestion. What transit advocates also ought to know is that more mass transit construction also tends not to reduce highway congestion. The cause of road congestion is that if your city is a thriving and vibrant place full of jobs and leisure activities, then space on a road is going to be a valuable thing. It’s a valuable thing that’s generally given away for free. Consequently, it tends to get overconsumed to the point where the traffic congestion itself becomes enough of a deterrent to prevent more people from pouring onto the road. Building more lanes or more mass transit options will initially alleviate the congestion, but the fact that the road is now less congested becomes a reason for more people to pour onto the road. By increasing the capacity of your transportation network, you increase the total quantity of people transported without really alleviating congestion.

There are two workable ways to permanently rid yourself of traffic jams, one sensible and one dumb. The dumb one is to massively overbuild transportation infrastructure. Not just too much infrastructure for right now, but infrastructure that so far outpaces your area’s needs that it won’t induce enough growth to catch up. A “bridge to nowehre” kind of thing. The sensible one is to build the amount of transportation infrastructure that your area needs and charge money for its use. If the crowded suburban commuter routes in the D.C. area had congestion pricing at peak times, then the roads wouldn’t be so crowded. And the revenue would become a valuable source of funding for maintaining and expanding the area’s transportation infrastructure. And then people could pay lower taxes or we could hire more cops and teachers. But absent congestion pricing, a growing metropolitan area with a viable economy is never going to actually build its way out of road crowding, and that’s true whether you build highways or mass transit.