But that spillback effect never really took place.

That is "spillback."

(Strictly defined, gridlock occurs when spillback ties up traffic around an entire square block and offending drivers end up pretty much blocking themselves.)

Now, with business and tourism in New York booming, traffic experts say congestion in Manhattan is probably at its highest ever and spillback at its worst.

An hour later, as the chaos of spillback delays began to subside, thousands of people were herded out of the terminal after someone noticed an unattended knapsack by a food cart.

"Sometimes it seems like it's just going to stop for good," said Bob Milton, 59, who has driven a bus in Manhattan for 16 years and got his first spillback ticket during a crackdown last Christmas.

In 1931, when the Empire State Building was opened, there was a belief that office construction would never reach north of 59th Street; the assumption was that there would be a terrific spillback.

The slaying of two detectives near La Guardia Airport forced police investigators to close Grand Central Parkway to westbound traffic for nearly two hours yesterday afternoon, and the spillback caused traffic jams throughout much of northwestern Queens.

TRANSYT-7F combines a detailed optimization process (including genetic algorithm, multi-period, and direct CORSIM optimization) with a detailed macroscopic simulation model (including platoon dispersion, queue spillback, and actuated control simulation).

A more modest measure started in May and still in effect - reversing traffic flow on 33d Street between Fifth Avenue and the Avenue of the Americas - appears to have helped, or at least not hurt, the traffic flow by curbing the spillback that causes gridlock.

As of late last week, that question was probably on the lips of 6,552 drivers who had been caught on just three days in the city's latest crackdown on the scourge of gridlock, or what traffic specialists call "spillback," in which a single intersection is blocked by cars that fail to get through before the light changes.