Type 2 school buses constructed on and after July 1, 1970, shall have at least one emergency exit to the rear of a line drawn crosswise to the bus directly to the rear of the driver's seat. When the required emergency exit is not located at the rear of the bus, emergency exits shall be provided on both the left and right sides. Emergency exits shall provide at least 564 sq in. of escape area with a minimum dimension of 12 in.