Maybe it all began with O.J. Simpson and his white Ford Bronco. Or when every local television station started using helicopters to cover anything that remotely resembled news. Or maybe a city so tangled in freeways and addicted to driving just can't ever resist a wild chase.

Police pursuits have become such a constant spectacle here in recent years that about 2,000 residents pay $5 a month to subscribe to a service that alerts them by pager or e-mail as soon as another chase is broadcast live on television. Hundreds occur every year, far more than in any other city.

But life as Los Angeles has come to know it is about to change.

The city's police commission decided a few days ago to put the brakes on most of the chases that officers initiate, saying the practice has become too reckless. Officers can still pursue suspects wanted for serious crimes, but only in rare instances will they be allowed to chase motorists who commit traffic infractions, such as running a stop sign.

The policy change was made at the urging of Police Chief William Bratton, a newcomer to the city who sounds both mystified and alarmed by its chase mania and is scolding local television stations for hyping police pursuits with breathless, marathon coverage.

"It's become a form of entertainment," Bratton said in an interview. "Everyone has gotten too caught up in it. But the risks of many of these chases, to the public and to our officers, often far outweigh their law enforcement value."

The strict new rules may cut the number of police pursuits in half. Last year, there were more than 600 around Los Angeles, and although most ended in a whimper, some resulted in crashes that seriously injured and even killed innocent by- standers.

Last month, a car fleeing police here smashed into a minivan and severed the arm of an infant boy who was a passenger. A 4-year-old girl also was killed in downtown Los Angeles last year as the result of a police chase. Police say that in the past two years chases have led to more than 100 serious injuries and six deaths.

"This step is long overdue," said Ramona Ripston, executive director of the American Civil Liberties Union of Southern California, which has been calling for a crackdown on police pursuits for years. "The number of pursuits keeps rising, and so are the dangers."

No one really knows why chases have become such a pastime here. Some point to the surreal Friday night in 1994 when an apparently suicidal Simpson led Los Angeles police on an epic chase that much of the country watched unfold live. Since then, local stations here -- there are seven -- have almost never failed to win big viewer ratings when they break into programming to cover police pursuits. All the attention, officials here say, has led some police officers to believe they should always give chase when they see a crime or traffic violation. Some suspects also seem to delight in their sudden fame when they flee.

Chases that begin even with the smallest infractions sometimes last for hours, block major roads, paralyze rush-hour traffic and are covered with comic news media intensity.

In some instances, police have had a hard time negotiating with suspects at the end of chases because of noise from the swarm of news helicopters overhead. One chase carried live on local television a while back, involving a sport-utility vehicle that kept rolling on a highway even without one of its wheels, led local stations to interview car dealers later that day about the vehicle's durability under extreme conditions.

Ken Kuwahara, the proprietor of Pursuit Watch, the paging service for televised chases, said that, on average, local stations broadcast four police pursuits a month. He does not expect that habit to change, despite the new policy.

"There will still be many chases involving serious crimes," he said, "and many people find watching them emotionally compelling."

But Bratton said that he wants the police department to rely much more on its fleet of 15 helicopters to track fleeing suspects.

The new policy, he said, will not preclude police officers from chasing traffic scofflaws under certain circumstances, such as if a license plate check shows that a suspect is wanted for other offenses.

But the days of perennial pursuits around Los Angeles appear to be over.

"I'm sorry," Bratton said, "but I'm not responsible for ratings."

-- Rene Sanchez

A transit bus sits among debris after it was hijacked by a gunman and chased by police last spring in Los Angeles. One person was killed and six were injured.