Last year, the 13th National Conference on School Transportation (NCST) approved a 361-page document called National School Transportation Specifications and Procedures. The document proffers recommendations on equipment and operations, including a section on school bus wiring, which is reprised here. To order a copy of the document, contact the Missouri Safety Center, Central Missouri State University, Humphreys Ste. 201, Warrensburg, MO 64093. Or you can call (660) 543-4830. A. All wiring shall conform to current SAE standards. B. Circuits
1. Wiring shall be arranged in circuits, as required, with each circuit protected by a fuse or circuit breaker. A system of color and number coding shall be used and an appropriate identifying diagram shall be provided to the end user, along with the wiring diagram provided by the chassis manufacturer. The wiring diagrams shall be specific to the bus model supplied and shall include any changes to wiring made by the body manufacturer. Chassis wiring diagrams shall be supplied to the end user. A system of color-and-number coding shall be used on buses. The following body interconnecting circuits shall be color-coded as noted:
FUNCTION -- COLOR
Left Rear Directional Lamp –- Yellow
Right Rear Directional Lamp -- Dark Green
Stop Lamps -– Red
Back-up Lamps -- Blue
Tail Lamps -– Brown
Ground –- White
Ignition Feed, Primary Feed -– Black
The color of the cables shall correspond to SAE J 1128. 2. Wiring shall be arranged in at least six regular circuits as follows:
a. Head, tail, stop (brake) and instrument panel lamps
b. Clearance lamps and stepwell lamps that shall be actuated when the service door is open
c. Dome lamps
d. Ignition and emergency door signal
e. Turn signal lamps
f. Alternately flashing signal lamps
Any of the above combination circuits may be subdivided into additional independent circuits.
4. Heaters and defrosters shall be wired on an independent circuit.
5. Whenever possible, all other electrical functions (such as sanders and electric-type windshield wipers) shall be provided with independent and properly protected circuits.
6. Each body circuit shall be coded by number or letter on a diagram of circuits and shall be attached to the body in a readily accessible location.
C. The entire electrical system of the body shall be designed for the same voltage as the chassis on which the body is mounted.
D. All wiring shall have an amperage capacity exceeding the design load by at least 25 percent. All wiring splices are to be done at an accessible location and noted as splices on the wiring diagram.
E. A body-wiring diagram of a size that can easily be read shall be furnished with each bus body or affixed in an area convenient to the electrical accessory control panel.
F. The body power wire shall be attached to a special terminal on the chassis.
G. All wires passing through metal openings shall be protected by a grommet.
H. Wires not enclosed within the body shall be fastened securely at intervals of not more than 18 inches. All joints shall be soldered or joined by equally effective connectors, which shall be water- and corrosion-resistant.
