Tail and Stop (Brake) Lamps. Two tail and stop lamps having an illuminated area of not less than 19 square inches shall be mounted on the rear of the vehicle at a height not less than 15 inches and not more than 72 inches above the surface on which the unloaded vehicle rests and shall be positioned as far apart as practicable. Turn Signal Lamps. Turn signal lamps may be independent units and shall be equipped with a four-way hazard warning signal switch to activate simultaneous flashing of the turn signal lamps when needed as a vehicular traffic hazard warning. Surface mounted, amber clearance lamps, with a minimum of 4 candlepower each, shall be mounted on the sides of the body at approximately seat level rub rail height just to the rear of the service door on the right side, and approximately the same location on the left side, and shall be connected to function with the regular turn signal lamps. Back-Up Lights. Two back-up lights shall be installed to be activated when the gear shift lever is placed in reverse. The lights shall be not less than 4 inches in diameter with a minimum of 32 candlepower and mounted above the bumper and below the window line. Clearance, Side-Marker, and Identification Lamps. Two red clearance lamps on the rear and two amber clearance lamps on the front shall be mounted as high as practical on the permanent structure of the school bus to indicate extreme width. Two side marker lamps, amber at the front and red at the rear, shall be mounted on each side of the bus. Three red identification lamps shall be mounted on the same level not more than 8 inches apart in the center rear of the body as high as practical, and three amber identification lamps shall be likewise mounted in the center front of the body. Interior lamps shall adequately illuminate the entire aisle, the emergency passageway, and the stepwell. Circuits. Wiring shall be arranged in at least ten regular circuits as follows: Head, tail, stop (brake), and instrument panel lamps; Clearance and stepwell lamps; Dome lamps; Starter motor; Ignition and emergency door signal; Turn signal lamps; Alternately flashing red and amber warning signal lamps; Horn and wipers; Heater and defrosters; and Hydraulic or electric lift, if equipped. The combination circuits listed in §F(1) of this regulation may be subdivided into independent circuits. Each body circuit shall be coded by number or letter at 4 inch intervals or by color. The code shall appear on a diagram of the circuits in a readily accessible location. Wiring Protection. Wires within the body shall be insulated and protected by a covering of fibrous loom, or its equivalent, which shall protect them from external damage and minimize dangers from short circuits. Whenever wires pass through the body or chassis members, additional protection in the form of a grommet or other appropriate type of insert shall be provided. Exposed wires are not permitted. Wires shall be fastened securely according to manufacturer requirements, and joints shall be soldered or joined by equally effective connectors. Switches. A solenoid switch or an electronic control system shall be connected to the ignition switch so that body accessories cannot be operated when the ignition switch is off. The alternating flashing warning lights, wheelchair lift, and electric powered service door, if equipped, may operate independently of the ignition switch. A noise reduction off and on switch shall be installed to permit the driver to shut off the body heater and fan motors. This requirement applies to school vehicles constructed as of the effective date of this regulation.