Frank Williams figures people who never drink and drive should pay less for car insurance than people who do. Three years ago, he started an association of people willing to sign a pledge not to drink and drive in exchange for lower auto insurance rates.

"That's ridiculous," said Bill Dodd, spokesman for the American Automobile Association of Florida. "How are you going to prove you're not going to drink and drive?"No insurance company licensed to do business in Florida offers a discount to people making a pledge, records from the Florida Department of Insurance show.

But Mr. Williams, a former accountant and manager of an asbestos removal firm, has persuaded more than 7,800 people - mostly Florida residents - to join his Safe Drivers Association of America. In company literature, he says members can qualify for a discount of as much as 30 percent off their auto insurance by signing the pledge.

Most insurance companies offer a discount to safe drivers based on driving record. Some also offer discounts for anti-theft devices and air bags, but not for making pledges, said Karen Chandler, spokeswoman for the insurance department.

"In a perfect world, that would be great," said Bill Sirola, spokesman for State Farm Insurance Co. "We could be in a position to offer a discount to anyone who pledges not to speed, too."

Mr. Williams' idea is noble, Mr. Sirola said. "But it would be unworkable and unmanageable from our point of view."

Mr. Williams says he expected that attitude from the major companies.

''As our membership grows, we'll have more clout," he said.

Mr. Williams expects the Safe Drivers membership to grow to "several million" in five years. With 3 million members paying a $40-a-year membership, Mr. Williams' association would make $120 million a year - money enough to exert pressure on the insurance industry, Mr. Williams said.

For now the association only offers its members the opportunity to call an insurance agent - who will quote them new rates.

Some members will save by dropping uninsured motorist coverage if they already have hospitalization insurance.

Some will save by claiming all the discounts they are entitled to, such as those offered for accident-free driving records. Some will simply get a lower rate from a different company. None get special rates simply for being members of the Safe Drivers Association, however.

That may surprise some members.

Jean Wieloch, the manager of Hillsboro Center Executive Suites in Deerfield Beach, Fla., where Mr. Williams is based, said she saved $300 on her annual insurance premium when she joined.

''You promise not to drink and drive. We promise you'll save money," says an advertisement for the association in USA Today.

A spokesman for Amstar Insurance of Miami, the company insuring Ms. Wieloch, said the discounts it offers are not limited to Safe Drivers members, and have nothing to do with whether they pledge not to drink and drive.