NASHVILLE, Tenn. — A crash that killed five children in Tennessee is reviving discussion over whether school buses —considered among the safest vehicles on the road because of their height and bulk — should also be equipped with seat belts.

Only six states require seat belts on large buses. Many others, including Tennessee, have considered but dropped such legislation in recent years out of concerns including cost.

Among those saying it is now time to reconsider is Tennessee state Rep. Joanne Favors, who responded to the scene of Monday’s crash in Chattanooga and was shaken by the sight of the yellow bus on its side, sliced through by a tree. Police said the driver, who has been charged with five counts of vehicular homicide, was speeding along a narrow, winding road when he crashed.

The bus did not have seat belts, and NTSB officials said it was too soon to know whether they would have made a difference.

Seat belt legislation introduced after two students and an aide died in a 2014 school bus crash in Knoxville did not make it out of committee, said Favors, a Chattanooga Democrat.