>>The people commuting by car to Manhattan are among the most skillful - and ruthless - drivers in the world.
>>Definitely not for the faint of heart.
>>I'd be willing to bet that in the ten years that I drove I never saw more than 4 feet of space between the front and rear bumpers of two cars during rush hour.
>>Not much slack in that system

How quick are they moving? There's a whole science now looking at those waves of speed up-slow down traffic on rush hour freeways, or miles of dense traffic dawdling along with no obvious cause, no accident, and no benefit to anybody. Studies suggest that hesitant lane-changing/merging behavior sets up standing waves of braking/accelerating traffic that perpetuate long after the incompetent driver (who invariably perceives their own behavior as "safe") has exited the freeway. Experts now say that traveling below the speed limit or slowing down unnecessarily to change lanes or merge, is more dangerous than speeding.