A crossing arm may be installed on the far right of the front bumper. The crossing arm: Shall be securely bolt-mounted; Shall be easily removable for towing; Shall be activated simultaneously with the stop arm; May not open more than 90 degrees; Shall extend a minimum of 66 inches from the front of the bumper when activated; May not have sharp edges or projections which may cause injury to students; and Shall be air, vacuum, or electrically operated and may not have lights. Interrupt Switch. A crossing arm interrupt switch may be installed on the dash near the control box for the alternating flashing lights. Pressing the switch shall stop the arm from opening for a full cycle and the arm shall recycle after the alternating flashing lights have been deactivated.