The Bush administration is requiring smaller school buses to be equipped with three-point, lap-and-shoulder seat belts for the first time.

Under new safety rules announced Wednesday, the government also will require larger buses to have higher seatbacks.

The lap-and-shoulder belts will be required on all new buses purchased in three years. Smaller buses currently are required to have lap belts. Seat belts are not required on larger school buses.

Transportation Secretary Mary Peters told The Associated Press that the equipment changes were prompted by a November 2006 bus crash that killed four students near Huntsville, Alabama.

Peters says the government is not requiring seat belts on larger buses because they would limit the number of student passengers.