This is a great idea.
According to a recent analysis of NYC traffic, 56% of all auto trips in NYC are 3 miles or less. Those trips could easily be replaced by public transit, bicycles or even walking in many cases! And apparently "for the region as a whole, 80% of auto commuters have a transit option that would take no more than 15 minutes longer than their auto trip." So lots of these people driving into NYC don't need to be driving.
http://www.streetsblog.org/2007/04/1...-city-in-flux/