NEW YORK -- If you savor white-water thrills but can't get away to the back country, try crossing a street in midtown Manhattan. Riding the rapids here means attempting the treacherous 100 feet from the east corner of Lexington Avenue to the west corner, or moving across the vaster uncharted waters of Broadway.

Whatever the street, the presumed equivalent of a life jacket is a green light and a walk sign. The safety is illusory because the old guarantee that traffic will stop for a red light is gone.

Between the sidewalks of New York, street anarchy has arrived in the societal pact that the yellow light, which once meant slow for a halt, is now an invitation to gun it for a sprint. Motorists get yellow fever from about 200 yards out. Shut sulking in their cars because of earlier red lights they couldn't roar through, they will now settle the traffic score by playing Mario Andretti turbocharging ahead in a personal high-speed chase against the odds.

A few beat them. Most don't. But it doesn't matter. The police are uninterested. Red-light running, which in quainter times was called lawlessness, means that jungle laws have replaced traffic laws. In the Car Wars of New York, pedestrians survive less with footwork than with headwork: mentally preparing themselves for the worst because that's what they'll probably get.

In the first 10 months of 1986, 23,899 pedestrians in New York's five boroughs were injured or killed at intersections with lights. All large cities have become dragstrips. No form of government regulation is as close to the lives of citizens as traffic signals, except the government relies on the public to be self-regulating. The high number of bodies and bones sacrificed in New York says that cars are king on the royal road to gore.

Earlier this year, a group of citizens decided that if the police can't, or won't, enforce traffic rules maybe cameras will. Wendy Lehman, a Manhattan artist who lives on Fifth Avenue and thinks that every crossing of the street to Central Park shouldn't need the intercession of St. Christopher, organized the Stop Traffic Offenses Program (STOP). The organization advocates the use of photographs to issue tickets to red-light runners. A car's rear license plate would be caught on cameras installed at intersections.

STOP went forward with its idea and managed to get it to the floor of the New York legislature. The organization might have been dismissed as one more group of wheel-spinners except that traffic cameras have been saving lives in such countries as Canada, West Germany and Switzerland. STOP, which initially thought that state legislatures are ruled by reason, found that high principles have less power than high rollers. Its bill, which passed the state senate 51-5, lost in the assembly. ''It was largely because of lobbyists hired by the car rental industry,'' Lehman says. ''We're going back next session with our bill, but this time we'll have a lobby of our own in place.''

Lehman, the chairperson of STOP, was radicalized into action one springtime morning in 1982 when taking her children to school. They were on a crosstown bus. While passing through an intersection at Lexington and 86th, Lehman happened to look out and see a little girl lying on the sidewalk. She had been hit by a van that had run a red light. A pedestrian, a state assemblyman it turned out, was putting his tie around the child's leg to stop the bleeding. Lehman learned later that the injured girl, who spent three weeks in intensive care, was a schoolmate of her daughter's.

Lehman went to the mayor's office, which advised STOP to stop complaining and raise money so it could buy traffic-safety coloring books for children. This ingenious solution had one flaw: the colors red, yellow and green are a rainbow of irrelevance. There is no longer a way to teach children to cross the street. Lehman reports that her husband, currently on crutches, has no way of safe passage either.

Short of renting armored tanks to move around, camera enforcement, backed by heavy fines and license revoking, is the last option for safety. In Southern California, say this much for the freeway war zones, in which four people have been killed by fast-lane gunplay: the combat is restricted to motorists. In New York, it's the unfair fight of cars against pedestrians.

The mayhem explains one curiosity, the popularity of the New York marathon. The autumn event, which draws 20,000 people and turns away another 40,000, is the only day of the year when the streets are safe for walking, provided you run 26 miles.