"Companies will now be responsible for all their policies, forcing responsible management of losses and a greater incentive to fight fraud in the marketplace, which means lower rates for drivers," she said.

Currently, insurance agencies rather than individual drivers are assigned to insurance companies. Those companies are required to accept all business presented by the involuntarily assigned agencies, regardless of the volume of business or the amount of losses they produce.

Frank O'Brien, regional manager for the Property Casualty Insurers Association of American, said the new plan was a good first step for an insurance market in need of overhaul. "The Massachusetts auto insurance market is collapsing, and Commissioner Bowler's rules are a necessary and a good first step on the road to restoring stability to the market and in attracting new companies with needed additional capital to the insurance business here," he said in a statement.

John Murphy, American Association vice president, said the plan brings Massachusetts into alignment with 43 states.

The law will go into effect April 1 for newly licensed drivers or those coming in from out of state. It will expand in increments over a three-year period.

Two insurance companies serving the state along with consumer groups have opposed the plan and will urge the incoming Democratic administration of Gov.-elect Deval Patrick to slow the implementation.

Stephen D'Amato, a consultant to the Cambridge-based Center for Insurance Research, said the new assigned risk plan will not work with the current "fix and establish" system, in which the department mandates the auto rates each year.

He told the NU Online News Service that eventually the new governor will have to look into delaying implementation to study the consequences of the program.

"And I think it is most important that any decisions about who to put in the assigned risk plan be made on driving record only, and not on other factors based primarily on income," he said.