10 steps to a better lighting system specification


Gone are the days when you could significantly improve your lighting performance by simply adding LED safety lighting to truck bodies. After all, LED safety lighting has been available since the early 1990s.

Now that we have settled into the next millennium, we need to add some options that will continuously improve the robustness of the lighting system. A few inexpensive improvements in the design phase hold the promise of long-term savings and system reliability for the future.

When looking at a medium duty truck, the first consideration needs to be the electrical supply of the truck chassis to the truck body. Evaluate what is the nominal voltage, the circuit protection strategy and the electrical connection system that is used to connect the wiring from the chassis to the body.

The following is a checklist based on Truck-Lite’s experience that can be used to improve the specification of the vehicle lighting system.

1. Get the suppliers involved (chassis, body and lighting supplier) in the development of a fleet specification. A short meeting with them will go a long way to ensure a reliable, robust specification. 

Also, review the past failure mode data that was experienced for that specific class of vehicle to provide continuous improvement opportunities and look for opportunities through specification that can be improved.

2. Understand the type of nominal electrical voltage supply and the type of circuit protection system that is being planned. When there was only incandescent safety, there wasn’t a big concern because incandescent bulbs are nothing more than glowing fuses. 

With today’s LED electronic systems that draw only 20 percent of the amperage, a new, fresh look at the circuit protection is necessary.

3. Pay attention to the chassis connector. A great deal of work has been done recently by the Technology and Maintenance Council (TMC) to develop a standardized industry recommended practice for this: TMC RP 1427, Standard Body-to-Chassis Connector. This is designed to assist truck chassis manufacturers, truck body manufacturers and equipment users with the design and manufacture of end-of-frame (EOF) chassis connectors. 

Strong consideration should be used during the development of a connector for this application.

4. Consider body wiring specifications.  As far as a wiring specification for a truck, Truck-Lite recommends starting with TMC RP, 1404 Wiring Standards for the Light and Medium Duty Chassis/Body Interface. This recommended practice is intended to help light and medium duty truck chassis and body manufacturers standardize the truck chassis-to-body wire interface on commercial vehicles.

Selecting a lighting supplier that also makes the wiring harness will help ensure continuity with the reliability of a vehicle electrical system.

5. Reduce damage to wire and connectors. Route the wire and connectors on the inside of the body to reduce impact of spray and physical damage. Installations following this simple specification often have wire harnesses that last the life of the vehicle. 

6. Consider the proper location of the safety lighting system. This often can be a challenge because of all of the different equipment that can be added to a truck body.  One of the most frequent challenges is how to properly install the lighting and reflex reflectors on vehicles equipped with liftgates. 

Often, the liftgates are located in an area which is also the most common lighting installation location. This can be a dilemma as there are frequent areas where the safety lighting systems can be blocked or rendered less effective. 

A good resource for helping determine the location for the lighting is TMC RP 1430, Lamp and Reflector Placement for Light and Medium Duty Vehicles with Liftgates.

7. Watch for physical damage risk areas. The primary reason for lighting failure on medium duty trucks is physical damage. A small amount of time spent on selecting quality LED lights that are protected from physical damage can ensure a much longer life. 

Tree branches often are a primary source of physical damage. The selection of lighting products that are fully protected by an extrusion or corner cap is an effective way to limit physical damage.

8. Protect the rear lighting. Rear lighting is frequently mounted on the rear posts of the vehicle. It is important to install bumpers to ensure that they are contacting the dock seal or loading dock not the lighting.

The standard function of a medium duty truck dictates that someday, the vehicle will hit the loading dock much faster than was intended.

Reviewing the lighting locations and anticipating the necessary protection if this happens will ensure that the lighting will last the life of the vehicle.

9. Check the front corner caps. Some of the new plastic corner caps on van bodies may not provide adequate protection from physical damage from tree branches. For fleets that operate in an area that has a lot of hardwood trees along the roadways, engineer the lighting package to provide improved protection.

Corner caps made of casting materials often do a better job of protecting the truck body.

10. Corrosion is failure mode number two. The second most frequent failure mode for lighting on medium trucks is corrosion. Select quality LED products that have integrated sealed connectors to provide a long life and an adequate barrier to corrosion found on today’s roads. 

Use dielectric grease with electrical connections – as recommended by the manufacturer – to inhibit corrosion in your system.



With all of the improvements that are available through new products that have been developed in the last two decades, the trucking industry is nearing a time when you can “fit and forget” your lighting products for the life of the vehicle.

Brad Van Riper is senior vice president of research and development at Truck-Lite (www.truck-lite.com). The company is a major producer of signal lighting, forward lighting, wiring harnesses, mirrors, turn signal switches and safety accessories to the heavy duty truck, trailer and commercial vehicle industries.