Social Science. Passage:

"Economists once treated traffic congestion as a simple coordination failure: too many drivers choosing the same road at the same hour. The proposed cure was equally simple—add capacity. Yet the historical record is unkind to this logic. When a metropolitan region widens a highway, travel times fall briefly and then, within a few years, return almost exactly to their former level, now with more vehicles moving than before. The phenomenon, which transportation researchers call 'induced demand,' is not a quirk. It is the predictable result of a latent pool of trips that were never taken precisely because the road was congested. Reduce the cost of driving and that pool empties onto the new lanes. The widened road does not fail to relieve congestion despite being used; it fails to relieve congestion because it is used."