A study undertaken by Matthew Turner of the University of Toronto and Gilles Duranton of the University of Pennsylvania compared the total number of new roads against total miles driven in various U.S. cities between 1980 and 2000.
They found that new roads are the cause of new traffic, not the solution to existing traffic, and cities that have chosen to remove roads have seen benefits:
“After replacing the cars with a river, parkland, and some smaller roads, traffic didn’t get worse and many other things, including pollution, got better.”
The full article is over at Wired.