[akgerber]

That isn't right. NYC's trolleys/buses were more efficient in the pre-automobile era when there was much less other traffic to block them, but Manhattan is about two miles wide and about 15 miles long; covering even 10 miles in 10 minutes would mean travelling at 60mph on city streets without stopping, and mass transit obviously needs to stop at least every couple miles. The express subway lines still take you up & down the island as quickly as ever (about 25 minutes from 125th St. to the Battery, apparently).

Manhattan's mass transit system is largely intact from its peak (except for the incomplete Second Avenue Subway, to replace the demolished Second Avenue Elevated the East Side), and has become better integrated from the private era when there were three competing systems. The trolley lines were more significant in the outer boroughs, and could reach speeds & frequencies similar to their best years with proper implementation of modern light rail or bus rapid transit. That would require the political will to take away surface right-of-way from the (boisterous, wealthier) car-driving minority.