BOSTON - A proposal to link the mileage drivers put on their cars to the amount they pay for insurance is drawing criticism from those who believe the move unfairly favors those in cities.

"In cities, you can walk around," said Thomas Minichiello, who owns Bradford-based Minichiello Insurance Agency. "But in rural areas, even a pharmacy is sometimes 12 miles away."

Sen. Susan C. Tucker, D-Andover, also worries that rural areas may stand to lose if the bill is passed. Tucker, who as a state senator has focused on reducing the cost of auto insurance through fraud control, said more data is needed to prove drivers North of Boston don't see their premiums hiked as a result of the legislation.

"Show me the numbers," she said. "I haven't seen any yet."

Rep. Brad Hill, R-Ipswich, said many of his constituents drive to Lexington, Boston or even the South Shore, and their premiums would see large annual increases under the proposed law.

"You should never have to pay by how much you drive but by how you drive," Hill said. "We have a lot of very good drivers, and in my opinion why would you want to penalize those people?"

Tucker is on the Legislature's Financial Services Committee, which is currently considering two pay-as-you-drive bills. Their primary backers are Rep. Carl Sciortino, D-Somerville, and Rep. James Marzilli, D-Arlington.

The bills would allow the state's insurance commissioner to base insurance rates on a "pay-as-you-drive" or a cost-per-mile basis. The more a motorist drives, the higher the insurance rate. Both bills recommend that a study be conducted on the benefits of the plan.

If approved, the change wouldn't happen all at once. Sciortino's bill would phase in the change. For example, by Dec. 31, 2010, he wants the "pay-as-you-drive" policies to represent at least five percent of the policies that they sell.

California, Texas and Oregon are also considering similar bills. In Minnesota, "pay-as-you-drive" was introduced on a trial basis.

According to Marc Breslow, the co-chairman of the Massachusetts Climate Action Network, the Progressive Insurance Co.'s test of the system in Minnesota uses automobile computers, or so-called "black boxes," to measure mileage.

"I'm not sure at what stage the trials are in," he said. "But it's something to look out for."

Minichiello said pay-as-you-drive is already used in many countries in Europe, including the United Kingdom.

Stephen D'Amato, a consultant with the Cambridge-based Center for Insurance Research, said there are already incentives in place to drive less.

"For example, right now, if you drive 5,000 miles or fewer in a year, you get a 10 percent discount on your premium," D'Amato said.

D'Amato believes that the pay-as-you-drive bills are important.

"It's an interesting concept," he said. "The question is how you implement it."

What's important is that regulators don't set rates for rural drivers the same as urban ones. So, whatever rates are established would take into consideration that rural drivers have to drive longer distances and have less access to public transportation.

The bills have strong advocates among environmentalists in the state because they would offer incentives for motorists to drive less, creating fewer greenhouse gasses.

"The bill not only reduces pollution, congestion and possibly accidents," said Carrey Russel, staff attorney at the Conservation Law Foundation, "it also makes auto insurance more affordable."

Staff writer Stacie N. Galang contributed to this report.