One expect summed it up by saying: "Trying to cure traffic congestion by building more roads is like trying to cure obesity by loosening your belt." One study of 30 California counties over several decades found that, for every 10% increase in road capacity, traffic increased by 9% within four years.

One expect summed it up by saying: "Trying to cure traffic congestion by building more roads is like trying to cure obesity by loosening your belt." One study of 30 California counties over several decades found that, for every 10% increase in road capacity, traffic increased by 9% within four years.