Building New Roads Doesn't Decrease Traffic
The idea that traffic congestion is "demand" and will decline if we "supply" more roads is false. A new study finds that, in the words of the Wall Street Journal:
"All else being equal, a 10% increase in interstate mile-lanes built, in 2000, led to a 10% increase in vehicle-miles traveled [VMT]. New commercial traffic and additional trips by current residents made up the bulk of that increase."
That means that when taxpayers build a new urban road or highway, it will do virtually nothing to decrease the traffic on the old roads. The study calls this The Fundamental Law of Road Congestion, and lumps public transit with new roads.
"If we were to somehow remove a subset of a city’s drivers from a city’s roads, others would take their place. We can think of public transit in this way. Public transit serves to free up road capacity by taking drivers off the roads and putting them in buses or trains. But the fundamental law implies that the provision of public transit should not affect the overall level of [VMT] in a city."
America's taxpayers are facing tremendous needs ($2 trillion est.) for road, bridge, and other infrastructure repairs. But it's useful to know that, despite the Highway Lobby's claims that building roads cuts congestion and pork-seeking communities' appetite for new-construction jobs, the driving public won't get their money's worth from more Interstates and urban arteries.
Specific construction projects can free up road bottlenecks of course. And yes, there are many other reasons to encourage public transit. Travel costs are lower; parking costs are usually nil; riders can read or work (or text); and emissions are lower. But the study concludes:
"These ﬁndings suggest that both road capacity expansions and extensions to public transit are not appropriate policies with which to combat traffic congestion."
So what WILL reduce traffic congestion? The study points to one possibility.
"This leaves congestion pricing as the main candidate tool to curb trafﬁc congestion."
And who knows - rising gas prices might just have the same effect.