The upside of downshifting
Contrary to what highway planners generally predict, widening roads and building new highways actually causes, rather than relieves traffic congestion in metropolitan areas.
According to "Analysis of Metropolitan Highway Capacity and the Growth in Vehicle Miles of Travel,” expanding an area's road network can increase traffic up to 43%. The study also shows that highway congestion would have grown less rapidly if no new or wider highways were built at all.
The study used data from the Texas Transportation Institute's database for 70 urbanized areas from 1982-1996.