Transportation planning today suffers from several common fallacies, including the myth of the great streetcar conspiracy and the notion that we should spend billions of dollars on obsolete forms of transportation to give people “choices.” But the most troublesome myth is the notion of induced-demand, that is, that new roads will automatically become fully congested so there is no point in building any. That myth most recently came up in a recent op ed piece in the LA Times.
This idea makes no sense at all, yet it is widely believed by public officials and transportation planners. Saying that relieving congestion “induces” driving is like saying that building new maternity wards induces people to have more babies. If it were true that roads automatically become congested, then Interstate 80 would be as congested in Rawlins, Wyoming as it is in Chicago, and Interstate 90 would be as congested in Mitchell, South Dakota as it is in Seattle.