First, it doesn't work: The stimulus package, which leaned heavily on road construction projects, failed to produce the number of jobs it promised. In contrast, according to a new study by the Political Economy Research Institute in Amherst, MA, bicycle and pedestrian projects create more jobs per dollar than road projects. Similarly, transit investments stimulate nearly a third more jobs than road construction
Second, it won't lead to the future we want: Building highways is a 20th-century response to a 21st-century program. It may create some jobs in the short term, but in the long term, it will only contribute to greenhouse-gas emissions, create additional sprawl, and increase Americans' reliance on cars to get around. Additionally, every dollar spent on highways is a dollar that could have been spent on transit or bike facilities---two areas where spending has been lagging behind for decades.
How many more people would Metro be able to move around if it got a few hundred million more dollars, compared to the number of drivers a new highway would serve? Sadly, it looks like we won't get the opportunity to answer that important question.