When the express lanes projects on the I-495 Beltway and I-95 in northern Virginia are ready for commuters, they will be designed to serve a dual purpose: encouraging carpooling by giving HOV-3 vehicles a free ride, and reducing congestion by also giving motorists the option of paying a premium toll to escape the usually jammed non-toll lanes.
The first of those goals is attainable. But the second is not, according to an expert on drivers’ behavior, who says expanding two of the busiest highways in the Washington metropolitan region will produce the unintended consequence of more congestion in the long term.
“The biggest potential problem is that we’re building more roads that will provide very short-term congestion relief and will cause other kinds of traffic and travel problems,” says transportation consultant Rachel Weinberger, the co-author of Auto Motives: Understanding Car Use Behavior.
Weinberger believes enough drivers will be willing to pay the tolls so Transburban, the private entity building the 495 and 95 Express Lanes, will make a profit. However, she says, there's little evidence to suggest expanding highways will solve a region’s congestion woes.
“First we have to ask, do we really need this road? All of the research shows that when you add capacity to highways, rather than relieving congestion in the long run, you actually create more congestion in other parts of the system,” she says.
In short, wider highways induce more traffic. Those new users ultimately have to exit the highway somewhere, producing more traffic on secondary roads where expansion is not possible. “Now you have dumped more cars onto the streets on Washington D.C. because you’ve added this capacity on I-495,” Weinberger says.
Earlier this week, TN asked Virginia governor Bob McDonnell if northern Virginia is becoming overly reliant on highway expansion projects to solve congestion problems. McDonnell responded that the state is trying different solutions. “We are trying to do everything,” he said, adding that Virginia is investing in transit projects like the Silver Line.
Backers of the Express Lanes projects are relying on drivers’ willingness to pay pricey tolls for a faster, more predictable ride. They are also calling the possible increase in carpooling a win-win, even though more free rides on the new lanes mean less toll revenue for Transurban. However, in the contract with the state of Virginia, Transurban is protected in the event the number of free rides rises dramatically.
The state is required to subsidize ride sharing if the number of carpoolers on I-495 reaches at least 24 percent “of the total flow of all [vehicles] that are… going in the same direction for the first 30 consecutive minutes during any day… during which average traffic for [the toll lanes] going in the same direction exceeds a rate of 3,200 vehicles per hour…” The threshold on I-95 will be 35 percent under similar conditions.
In Weinberger’s view, there will enough new carpoolers and toll payers to provide the appearance of relief -- but it won’t last.
“We sit in traffic and we fume about it and we think that the easy solution is to build more lanes and then we won’t have so much traffic, but I am sure the Beltway has been expanded several times and there continues to be traffic,” she says. "Typically when we build more capacity we make somebody’s trip a little bit faster, but it’s very rare that people actually conserve their travel-time savings. Instead they’ll make some other adjustment like they may move further out, creating more sprawl."