If you happen to make a poor decision and drive back home at 2pm on Sunday after a long July 4th weekend, you end up cursing the crush of traffic and getting angry at the State of New Hampshire for not insisting on building more lanes on I-95. You make a simple deduction – if you just build more roads, traffic jams will magically evaporate. Turns out it is not that simple.
I recently read an article from Wired about road congestion and the fact that we can’t build our way out of traffic problems… because the roads themselves cause traffic! What happens is something called induced demand, which by increasing the supply of something makes people want that thing even more. There is some pretty significant data to back this concept up: basically every time we increase road capacity across America, the total number of miles driven in the area increases by the same rate. So if you build an extra 10% of roads, an extra 10% of miles are driven.
Another interesting tidbit is that the same thing happens when roads are reduced; so if you decide to close down a traffic lane – maybe to make a section of the city less car-focused and greener – the miles driven reduces itself correspondingly.
Ultimately traffic finds its own level.
True traffic solutions come when behavior can be modified – say for example by putting a cost on driving when traffic is at its worst. For example you put a congestion tax in place so that driving into a city during rush hour is subject to higher costs. If there are more roads people will naturally utilize them, but put a cost on using those roads at certain times and problems may be alleviated.