This sounds counterintuitive but is absolutely true. I know that London instituted a "tax" on all vehicles entering the downtown area, which helped greatly with

This sounds counterintuitive but is absolutely true. I know that London instituted a "tax" on all vehicles entering the downtown area, which helped greatly with the congestion. When I was visiting Munich I also saw that some roads were deliberately narrowed to discourage people driving. The infrastructure increase can never match the increase in number of vehicles. One can conjecture a modified version of Peter Principle: (Unless drastic measures are taken) traffic density will always increase to the level of congestion. Or think about the fact that regardless of how big your hard disk is, the rate it's being filled is generally constant. So, bigger roads doesn't make too much sense (there are also arguments from landscape beauty, i.e. remember how they demolished the Beijing Old Town for easier access, more roads mean more of that.)