LAWRENCE - Since being elected to her first term in 1998, state Sen. Susan Tucker promised her Lawrence constituents she would work hard to lower auto insurance rates that were among the highest in the state.

Yesterday, she was able to say she kept her word despite a long struggle she regards as one of her toughest on Beacon Hill.

"This is a great day for Lawrence drivers," the Andover Democrat said one day after learning that state Insurance Commissioner Julianne Bowler finally signed an agreement that will drop coverages city drivers pay for bodily injury by 20 percent more than the average state rate reduction.

It's not clear how much of a break city drivers will get on their insurance bills when the agreement takes effect next April because the commissioner won't set the overall rates until Dec. 15.

But Daniel Johnston, president of the Automobile Insurers Bureau of Massachusetts - one of the parties involved in the agreement approved by Bowler - has already estimated that the savings could amount to "hundreds of dollars or more" for many of those insuring their cars in the city.

The settlement - which was influenced in part by legislation filed by Tucker - was reached recently between the three entities involved in the state's auto insurance rate-setting process - the State Rating Bureau - an arm of the Division of Insurance; the attorney general; and the Automobile Insurers Bureau, which represents insurance companies.

Attorney General Tom Reilly announced the settlement more than a month ago, but Bowler balked at signing it until this week because she was interested in seeing additional information which did not involve Lawrence.

"I felt confident this was going to happen even when it was delayed," Tucker said in an interview yesterday.

"Now that it's actually signed, it's time for a celebration. I remember knocking on hundreds of doors in the city. People would actually bring out their insurance bills and I was astounded on how much people were paying," Tucker said.

"I've always told them getting lower insurance rates has been our top priority. Finally, the hard work, the tenacity and the teamwork paid off for the city," she said.

The commissioner's decision was spurred by the success of the city's auto insurance fraud task force - a multi-agency unit which has been credited with saving the insurance industry more than $30 million in reduced auto claims because of its three-year crackdown on fraud. More than 200 individuals have been charged with auto insurance fraud.

The industry-funded Insurance Fraud Bureau of Massachusetts, a partner in the Lawrence task force, has established task forces in nine other cities - including high fraud-prone neighborhoods in Boston - as a result of Lawrence's successful fraud-fighting efforts.

Bowler's decision finally recognizes that effort and gives other communities an incentive to follow Lawrence and reduce insurance fraud, Tucker said.

"Insurance companies have seen a reduction in claims of tens of millions of dollars," Tucker said. "The effort and time put in by Lawrence needed to be rewarded financially. This will show other communities there is real money in fighting fraud."

"I've been involved in many political battles but this is one of the longest, hardest fights I've won," Tucker said.

Lawrence police Chief John Romero hailed the commissioner's decision as "the real proof" of the task force's success.

"When we set out on this mission more than three years ago, I believed the ultimate success of our efforts would be based on not whether we can eliminate insurance fraud, but whether we bring down the rates," Romero said.

"It doesn't matter how many people we arrest. The true gauge of our success is whether those rates come down because of the reduced claims and the millions of dollars we have saved. The efforts of the task force have really paid off, I'm glad to say," Romero said.