First there's the screeching of tires.

Then comes the crash of metal on metal.

And finally there is the tinkle of falling glass as headlights and taillights crumble to the pavement.

These are the all-too-familiar sounds of motorists meeting by accident.

But to many Californians, these are also the sounds of opportunity knocking, according to auto insurers who say Californians are routinely abusing the insurance system by running up thousands of dollars in unnecessary medical bills and pain-and-suffering claims.

Simple but powerful incentives under California law--such as the ability to collect multiple medical benefits from several insurance companies for the same injury--are creating an atmosphere in which, the insurers say, an accident is not a tragedy but an opportunity to reap a financial windfall.

"It's like hitting the lottery," said Melville P. Windle, general counsel of 20th Century Insurance Co.

Industry officials say it is these claims that are the engine driving runaway auto insurance rates in California.

Trial lawyers and consumer advocates, most notably Ralph Nader, say that fraud is only part of the reason for high insurance rates.

Even the insurers concede that eliminating fraud altogether would not make insurance cheap. One industry estimate is that cleaning up the fraud problem would mean a 7% to 17% cut in auto insurance rates, while other estimates run as high as 30%.

Still, an examination of injury claims submitted to several California auto insurers reveals a pattern of large medical bills arising from even minor accidents--some so insignificant that there was no damage to any vehicle.

Files reviewed by The Times showed that medical reports often differed only in the name of the patient--with the diagnosis, cause, treatment and final billing amount almost identical to those of other patients visiting the same doctor.

And, curiously, the files showed that accident victims often did not visit their neighborhood family physicians, but rather chose to see doctors and chiropractors miles away, at the suggestion of their attorneys.

During the last 10 years, the rate at which Californians make claims against auto insurers for physical injuries has nearly doubled at some of the state's large insurers. The highest rates are recorded in metropolitan Los Angeles, where, on average, there is one bodily injury claim filed for almost every accident reported--more than double the pace found in rural areas or smaller cities such as San Diego--according to a study by 20th Century Insurance.