[lostmsu]

The idea is just not as obvious as you think. Take, for example, Manhattan in NY. If you compare the ratio of car/bus on its streets to a smaller city (I live in Seattle), it will be significantly lower. To the point that I am unsure removing cars altogether would change road conditions.

Now suppose we take all or majority of Manhattan's roads, let pedestrians in, and only allow buses, trucks, and utility vehicles. Suddenly buses are much slower than they are now, because the pedestrians have the right of the way.