For years, departments of transportation throughout the U.S. have spent billions of dollars on highway expansion projects. These projects are justified largely based on future forecasts that assume traffic volumes will continue to grow as they have in preceding decades. The problem with this is twofold: First, even if the forecasts are correct, widening highways or building new ones as a means of relieving congestion just does not work. What it does instead is to encourage more driving, a phenomenon known as "induced demand." The temporary gains of increased roadway capacity are ultimately negated as the highways inevitably become congested again, perpetuating a vicious cycle of wasteful expansion. Second, the forecasts have been completely wrong. Not only have traffic volumes not increased by the amount predicted, in most, cases they have been trending downward for the last 7 or 8 years. The end result is that transportation agencies are pursuing policies of expensive highway expansion despite data that does not support or justify these decisions. This also has the additional consequence of leaving less funding available for more sustainable forms of transportation investments, such as transit, bicycling, and pedestrian infrastructure as well as bridge maintenance, for which there is a great unmet need.
This problem can largely be solved if new Federal policies were put in place which changed the rules for how states compete for and are awarded transportation funding. Currently, states are rewarded for the kind of business as usual practices that attempt to "solve" traffic congestion by expanding highways. Instead, new criteria based on reducing carbon emissions and focusing on sustainability indicators should be developed which encourage less driving and increase mode choices. Using this criteria, most planned highway expansion projects would be replaced by greater investment for transit, bicycling, and pedestrian infrastructure projects, while most highway funding would be allocated to better maintaining, rather than expanding existing roadways. The result of this kind of policy reform would create pressure on state and regional agencies to design truly multi-modal, sustainable transportation systems.