It's a question some parents ask when their children go off to school or they see the inside of the state's ubiquitous yellow school buses: Why aren't seat belts required in school transportation vehicles to encourage students to buckle up?

New Bedford Rep. Antonio Cabral has been trying to get the state to require seat belts in school buses for the last ten years. Retrofitting existing buses would cost around $11,000 a piece, no small burden on school districts or bus operators.

"Small price to pay? Yes it is. I think we as a society, we as a community, we as a state have to determine is it worth the life of a child, is it worth the $11,000?... This is about the safety of our own children," Cabral said at a hearing of the Legislature's Public Safety Committee Tuesday.

The School Transportation Association of Massachusetts represents the companies that operate school buses. They've opposed the bill in the past, arguing that bus seats are already safe for riders. But now they say they could back the bill if there's enough lead time and if drivers are not held liable for injuries to children who aren't buckled up.