HARTFORD, Conn. — A state measure that cuts the sales tax on school buses equipped with three-point belts — but does not make them mandatory — has been signed into law.

Connecticut Gov. Jodi Rell approved the bill earlier this week. It was spurred by the death of a Rocky Hill high school student in a January school bus accident.

“This law provides a modicum of state assistance to districts wanting to add seat belts to their fleet but does not impose a costly new mandate on all districts — striking a good balance between incentive and choice,” Rell said.

The law, authored by Rep. Tony Guerrera, reimburses school bus operations for 50 percent of whatever they pay in the state’s 6-percent sales tax for new school buses equipped with three-point belts. The sales tax on a $100,000 bus, for example, would be $6,000, so the reimbursement would be $3,000.

The state Department of Motor Vehicles will begin offering the program in July 2011. It will be funded through a $50-increase in the fees paid for restoring suspended or revoked driver’s licenses, commercial driver’s licenses and vehicle registrations.

The program will run through at least 2018. During the 2018 legislative session, lawmakers will hold a hearing to decide whether it should be continued.

Earlier this year, another measure authored by Guerrera that would have required seat belts on new school buses was voted down by a committee because of cost concerns. But Guerrera was optimistic about the incentive measure.

“I believe all buses should have seat belts, but this is a step in the right direction,” he said.