When you're out on the road pulling your trailer, you want to be as safe as possible. One important component of towing safety is visibility - making sure other drivers can see your trailer. And lighting plays a big role in visibility. So, whether you're replacing a single light bulb or lens cover, or you're adding a complete set of lights to a homemade trailer, you want to get the right part for the job.
You also want to get lights that comply with the US government's lighting requirements for trailers. Based on standards developed by the Society of Automotive Engineers (SAE), the National Highway and Traffic Safety Administration (NHTSA) has developed requirements for vehicle lights. The set of regulations that applies to vehicle lighting is known as FMVSS 108, and it includes lighting requirements for trailers. These regulations define how many lights a trailer must have, where the lights should be located, what performance standards the lights must meet, and how manufacturers must label lighting components.
Note: The information contained in this article is based on the US government's regulations pertaining to vehicle trailer lighting. These regulations can be found under Title 49, Part 571, Section 108 of the Code of Federal Regulations. This section covers lamps, reflective devices, and associated equipment related to motor vehicles. To see these regulations and to get the most up-to-date information, visit the US government's Electronic Code of Federal Regulations.
This article will help you answer the following questions:
All trailers are required to have stop lights, tail lights, turn signals, and reflectors. Trailers that are 80" wide or wider, or that are 30' long or longer need additional lights and reflectors. A trailer that is 80" wide or wider and has a Gross Vehicle Weight Rating (GVWR) over 10,000 lbs requires conspicuity treatments. These treatments consist of strips of reflective tape or rows of individual reflectors that create an alternating pattern of red and white along the sides and rear of a trailer to make it easier to see.
To determine which lights a trailer needs, you need to know the trailer's overall length and width and whether the trailer's GVWR is greater than 10,000 lbs. If you don't know the dimensions of your trailer, you'll have to measure it. To find your trailer's GVWR, look for a sticker located somewhere on the trailer.
Measuring the Length of a Trailer
To find a trailer's length, measure from the rearmost point on your trailer to the point of the trailer closest to the vehicle. Be sure to include the coupler or any overhang in this measurement.
Measuring the Width of a Trailer
To find the width, measure at the trailer's widest point. This measurement must include any overhang or protruding fenders.
Locate Trailer GVWR
To find a trailer's GVWR, look on the trailer's tongue or frame for a label like the one seen below.
Once you know your trailer's length, width, and GVWR, you can use the following list to find the specific lights for your trailer.
Required Lights | |
---|---|
2 Stop/brake lights | These functions are frequently found together in combination tail lights. |
2 Tail lights | |
2 Turn signals | |
2 Rear reflectors | |
1 License plate light | |
2 Rear side marker lights | |
2 Rear side reflectors | |
2 Front side marker lights | These functions are frequently combined into a single side marker light. |
2 Front side marker reflectors |
Exceptions
Required Lights | |
---|---|
2 Stop/brake lights | These functions are frequently found together in combination tail lights. |
2 Tail lights | |
2 Turn signals | |
2 Rear reflectors | |
1 License plate light | |
2 Rear side marker lights | |
2 Rear side reflectors | |
2 Front side marker lights | These functions are frequently combined into a single side marker light. |
2 Front side marker reflectors | |
2 Rear clearance lights | Front and rear clearance lights can be combined on boat trailers. |
2 Front clearance lights | |
Rear identification lights | ID lights are often grouped into a single light bar. |
Exceptions
Required Lights | |
---|---|
2 Stop/brake lights | These functions are frequently found together in combination tail lights. |
2 Tail lights | |
2 Turn signals | |
2 Rear reflectors | |
1 License plate light | |
2 Rear side marker lights | |
2 Rear side reflectors | |
2 Front side marker lights | These functions are frequently combined into a single side marker light. |
2 Front side marker reflectors | |
2 Rear clearance lights | Front and rear clearance lights can be combined on boat trailers. |
2 Front clearance lights | |
Rear identification lights | ID lights are often grouped into a single light bar. |
Exceptions
Trailers 80" or Wider and over 10,000 lbs GVWR must have the following markings, which can consist of reflectors or reflective tape
Required Conspicuity Treatments |
---|
2 Pairs of rear upper body markings |
1 Continuous bumper bar marking |
1 Continuous rear lower body marking |
2 Continuous side markings |
Note: If conspicuity treatment would be placed at a location where a reflector would otherwise be required, the reflector may be omitted.
Required Lights | |
---|---|
2 Stop/brake lights | These functions are frequently found together in combination tail lights. |
2 Tail lights | |
2 Turn signals | |
2 Rear reflectors | |
1 License plate light | |
2 Rear side marker lights | |
2 Rear side reflectors | |
2 Front side marker lights | These functions are frequently combined into a single side marker light. |
2 Front side marker reflectors | |
Rear identification lights | ID lights are often grouped into a single light bar. |
2 Intermediate side marker lights | These functions are frequently combined into a single side marker light. |
2 Intermediate side marker reflectors |
Additional Lights for Trailers 80" or Wider | |
---|---|
2 Rear clearance lights | Front and rear clearance lights can be combined on boat trailers. |
2 Front clearance lights |
Exceptions
Trailers 80" or Wider and over 10,000 lbs GVWR must have the following markings, which can consist of reflectors or reflective tape.
Required Conspicuity Treatments |
---|
2 Pairs of rear upper body markings |
1 Continuous bumper bar marking |
1 Continuous rear lower body marking |
2 Continuous side markings |
Note: If conspicuity treatment would be placed at a location where a reflector would otherwise be required, the reflector may be omitted.
US regulations specify where lighting must be installed on trailers. The following list gives general rules that apply to all trailer lighting. And the following table shows rules that apply to specific types of lights.
Proper Mounting Locations of Trailer Lighting
Light | Location | Position |
---|---|---|
Tail lights * |
| 15" - 72" above the ground |
Brake lights * |
| 15" - 72" above the ground |
Rear turn signals |
| 15" - 83" above the ground |
Rear reflectors * |
| 15" - 60" above the ground |
License plate light |
| Varies based on position of license plate |
Rear side marker lights |
| 15" or more above the ground (On trailers 80" or wider, no more than 60" above the ground) |
Rear side reflectors |
| 15" - 60" above the ground |
Front side marker lights |
| 15" or higher above the ground |
Front side reflectors |
| 15" - 60" above the ground |
Intermediate side marker lights |
| 15" or higher above the ground |
Intermediate side reflectors |
| 15" - 60" above the ground |
Rear clearance lights |
| N/A |
Rear identification lights |
| N/A |
Front clearance lights |
| N/A |
* If only 1 light is used on a trailer less than 30" wide, it should be as close to the vertical centerline as possible.
Rules That Apply to Trailer Lights and Reflectors
Proper Mounting Locations of Conspicuity Treatments
Conspicuity Treatment | Location | Position |
---|---|---|
A pair of white reflective strips at each upper corner marks the rear upper body |
| N/A |
A strip of alternating red and white tape (or reflectors) marks the rear bumper bar |
| N/A |
A strip of alternating red and white tape (or reflectors) marks the rear lower body |
| 15" to 60" above the ground (height measured at horizontal centerline of strip when trailer is at curb weight) |
A strip of tape (or reflectors) marks the sides of the trailer |
|
15" to 60" above the ground (height measured at horizontal centerline of strip when trailer is at curb weight) |
Code Markings Required on Conspicuity Tape and Reflectors
Reflective marking tape must be marked with codes "DOT-C2", "DOT-C3", or "DOT-C4" on each white or red segment and at least once every 12" on all-white tape. Reflectors to be used in place of tape must be marked "DOT-C".
Rules That Apply to Conspicuity Treatments
US regulations call for conspicuity treatments to be added to trailers that are 80" or wider and that have a GVWR greater than 10,000 lbs. Conspicuity treatments consist of reflectors, reflective sheeting (tape), or a combination of both.
Apply to a Flat Surface
Proximity of Conspicuity Tape to Lights
Splitting Marking Tape to Clear Rivets or Other Obstructions
Red and White Marking Tape
Reflectors Used in Place of Tape
Trailer lighting must meet performance standards that are specified by US regulations. These regulations spell out what colors lighting devices must be, how they must be tested, how they must perform, and how they should be labeled. The following list and table show what information is typically included on lights, reflectors, and reflective tape. This information is usually molded into the cover of a light or reflector, and it is printed on the reflective tape.
Information Indicated on Lights, Reflectors, and Reflective Tape
SAE Codes on Trailer Light Lens
The SAE codes on the lens of the light pictured above indicate that this light can perform more than 1 function. Many trailer lights are designed to do this. Based on the SAE codes on this light, it performs the following functions.
Trailer Lighting and Conspicuity Tape Codes
Function | Color | Code |
---|---|---|
Tail lights | Red | T |
Stop/brake lights | Red | S |
Rear turn signals | Red or amber (yellow) | I |
Rear reflectors | Red | A |
License plate light | White | L |
Rear side marker lights | Red | P2, PC, P3, or PC2 |
Rear side reflectors | Red | A |
Front side marker lights | Amber (yellow) | P2, PC, P3, or PC2 |
Front side reflectors | Amber (yellow) | A |
Intermediate side marker lights | Amber (yellow) | P2 or P3 |
Intermediate side reflectors | Amber (yellow) | A |
Rear clearance lights | Red | P2, PC, P3, or PC2 |
Rear ID lights | Red | P2 or P3 |
Front clearance lights | Amber (yellow) | P2, PC, P3, or PC2 |
Rear upper body markers | White | |
Bumper bar markers | Alternating red and white | |
Rear lower body markers | Alternating red and white | |
Side markers | Alternating red and white |
What is the difference between lights that have a "C" in the code (PC and PC2) and those that don't (P2 and P3)?
The light beam emitted from a P2 or P3 light spreads out 45 degrees to each side of its centerline for a total of 90 degrees of coverage. This beam pattern can be seen straight on, but it cannot be seen clearly from the side of the trailer. When mounted square to the front, sides, or back of a trailer, this kind of light provides adequate visibility.
The light beam emitted from a PC light spreads out 90 degrees to either side of its centerline for a total of 180 degrees of coverage. This beam pattern can be clearly seen when you are standing directly in front of the light, as well as when you are standing on either side of the light. This wide angle beam allows the light to perform not only as a front clearance light, for example, but also as a side marker light.
To perform its combined functions, a PC light must be properly mounted. Some lights are designed to be mounted at a 45-degree angle between the front and side or between the side and back of a trailer. You must mount these lights on a part of the trailer that provides this 45-degree angle. Other PC lights emit light through 2 lenses, 1 that faces toward the front or back of the trailer and the other that faces toward the side. These lights must be mounted square to the back or front of the trailer and at the outer edge so that the light will also be visible from the side of the trailer.
What does it mean when a trailer light is for trailers wider than 80"?
Trailers that are 80" (6' 8") or wider at the widest point require front and rear clearance lights and rear identification lights in addition to basic trailer lights. The clearance lights indicate the width of the trailer when it is viewed from the front and the back. To properly indicate the width of the back of a trailer, 1 rear clearance light is required at each side on the back of the trailer at the trailer's widest point. Both of these clearance lights should be at the same height and as high as possible unless identification lights are mounted at the top, in which case the clearance lights can be mounted lower. A light that functions as a rear clearance light can be designated as a light for 80" wide trailers, whether the light is combined with other functions or it is intended only as a clearance light.
Rear Clearance Lights Combined with Other Lights
If the bed of the trailer extends out past the wheels, then the back of the trailer would most likely be its widest point. In this case, you can use combination lights that are designed for trailers wider than 80" and that have the clearance lights built in. These lights would be mounted at the widest point of the trailer at the rear.
These combination lights are most commonly found on flat bed utility trailers. Rear clearance lights must be mounted low on these trailers because there is no place above the frame on which to mount the lights.
Rear Clearance Lights Separate from Other Lights
If the trailer's wheels extend out at the sides beyond the bed of the trailer, then the fenders most likely create the trailer's widest point. In this case, you can use standard combination stop lights, tail lights, and turn signal lights just for those functions and mount separate lights on the fenders to mark the rear clearance.
You would not use a combination light made for trailers greater than 80" for this application, even though the trailer is wider than 80". The rear clearance lights, though, could be designated for trailers that are 80" wide.
You wouldn't use combination lights that include rear clearance lights on a tall trailer either. The rear clearance lights on a tall trailer are mounted high on its body - away from the tail lights.
What's the Difference between Non-Submersible, Submersible, and Waterproof Lights?
Trailer lights differ in their ability to resist or tolerate water entry. Trailers that may be submerged, like boat trailers, should be equipped with lights that can handle being in water.
Non-submersible lights are not designed to be submerged. The lens may have a seal or gasket to help keep water out, but that may not be enough to guarantee that water won't get into the light assembly.
Submersible lights are designed to avoid damage if they are submerged. To improve the ability of a light to resist water damage, manufacturers use 1 of 2 methods.
Greg C.
11/13/2021
Question on the color requirement for the 3 rear cab/roof lights on my Jayco Hummingbird. The existing ones are red but I would like to replace with amber lenses due to not being able to find an exact replacement in red. The 2 in the front are amber. Color requirement for the rear?
Donna H.
10/3/2021
In Minnesota on an 8 foot wide trailer, can the rear lights be mounted on the outside edge of the trailer or will that make the trailer to wide for specs?
Alex E.
8/25/2021
The front and rear of my camper (80"+ wide, less than 30' long, less than 10,000 lbs) is rounded out (similar to a teardrop shape) with the farthest part being 18" longer than the top and bottom of the trailer (the part that sticks out the farthest is located 1/3rd the way up the trailer). Should I mount my identification lights and clearance lights 1/3rd of the way up the trailer since that is where it sticks out the most? If I mount it at the highest point it will be angled up.
"Another great purchase. Low prices, fast shipping and great customer service are always provided."
Evan W.
1/22/2023
21 foot boat trailer. Every video I’ve watched they run the ground shining lights straight in to the trailer wiring so they run when the trailer lights are on. Is doing this illegal to have blue lights under my trailer running constantly?