Trailer Lighting Requirements

Written by: Amber S

Last updated: 5/13/2024

Est read time: 17 mins.

Not to make light of the situation, but keeping your trailer visible is a pretty bright idea. (Sorry. It's out of my system.)

Safety and visibility are paramount, of course, but many of you are probably here because you don't want to get pulled over for a lack of proper trailer lights. If you're buying or building a trailer in need of some lights, you want to keep things legal and get the right lights for the job.

So what exactly are the legal requirements for trailer lighting? How many lights does your trailer need, where should they go, and what kind should you use? We'll break it down for you below.

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:

Are lights required on all trailers?
What lights are required on MY trailer?
Where do I mount these lights on my trailer?
What standards must trailer lights, reflectors, and reflective tape meet?
What is the difference between lights with a "C" in their code (PC and PC2) and those without (P2 and P3)?
What is the difference between lights that are for trailers wider than 80 inches and those that are not?
What is the difference between non-submersible, submersible, and waterproof lights?

Are Lights Required on all Trailers?

Yes, all trailers need lights to ensure safety and visibility on the road, although the required lights change a bit depending on the type and size of trailer you're towing and in which state. Here’s a quick rundown of the lights you’ll typically need:

Tail Lights
Turn Signal Lights:
Brake lights
Reflectors
License Plate Light
Side Marker Lights (to mark the trailer's length)
Clearance Lights (show width and height)

In general, these are the lights you'll typically need on most trailers. Keep in mind, however, that different trailers will need different lights, and most requirements are based on size. Below we'll go into more detail about what's required for each particular trailer size.

What Lights are Required on My Trailer?

All trailers are required to have stop lights, tail lights, turn signals, and reflectors. Trailers that are 80 inches wide or wider, or that are 30 feet long or longer need additional lights and reflectors. A trailer that is 80 inches 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 (like the one pictured below) located somewhere on the trailer.

1. Measure the Length of Your 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.

Measure trailer from rear-point of trailer to coupler

2. Measure the Width of Your Trailer

To find the width, measure at the trailer's widest point. This measurement must include any overhang or protruding fenders.

Measure width at the trailer's widest point

3. 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.

Gross Vehicle Weight Rating Label Example

Once you know your trailer's length, width, and GVWR, you can use the following list to find the specific lights for your trailer:

Trailer Type 1 = less than 80 inches wide and less than 30 feet long
Trailer Type 2 = 80 inches or wider, less than 30 feet long, and has a GVWR of 10,000 lbs or less
Trailer Type 3 = 80 inches or wider, less than 30 feet long, and with a GVWR greater than 10,000 lbs
Trailer Type 4 = 30 feet or longer (regardless of width or GVWR)

Required Lights for Trailers Less than 80 Inches Wide & Less than 30 Feet Long

1) Stop/brake lights (2)

Taillights (2)

3) Turn signals (2)

4) Rear reflectors (2)

5) License plate light (1)

6a) Rear-side marker lights (2)

6b) Rear-side reflectors (2)

7a) Front-side marker lights (2)

7b) Front-side marker reflectors (2)

Exceptions:

1. If your trailer is less than 6 feet long, you do not need to have front side marker lights or front side marker reflectors.

2. If your trailer is less than 30 inches wide, you only need to have 1 brake light, 1 tail light, and 1 rear reflector. These lights should be mounted at the center of the trailer, rather than on an outer edge.

Lights for trailers under 80" wide and under 30' long

Required Lights for Trailers 80 Inches or Wider, Less Than 30 Feet Long, & with GVWR of 10,000 lbs or Less

1) Stop/brake lights (2)

2) Taillights (2)

3) Turn signals (2)

4) Rear reflectors (2)

5) License plate light (1)

6a) Rear-side marker lights (2)

6b) Rear-side reflectors (2)

7a) Front-side marker lights (2)

7b) Front-side marker reflectors (2)

Exceptions:

1. If your trailer is less than 6 feet long, you do not need to have front side marker lights or front side marker reflectors.

Required Lights for Trailers 80 Inches or Wider, Less Than 30 Feet Long, and with a GVWR Greater Than 10,000 lbs

1) Stop/brake lights (2)

2) Tail lights (2)

3) Turn signals (2)

4) Rear reflectors (2)

5) License plate light (1)

6a) Rear-side marker lights (2)

6b) Rear-side reflectors (2)

7a) Front-side marker lights (2)

7b) Front-side marker reflectors (2)

8a) Rear clearance lights (2)

8b) Front clearance lights (2)

9) Rear identification lights

Exceptions:

1. If your trailer is a boat trailer, you can use dual-face lights that are yellow on one side and red on the other for the front and rear clearance lights. Usually, this kind of light is mounted on the trailer's fender with the yellow side facing toward the front of the trailer and the red side facing toward the rear of the trailer.

Required Lights for Trailers 30 Feet or Longer (Regardless of Width or GVWR)

1) Stop/brake lights (2)

2) Tail lights (2)

3) Turn signals (2)

4) Rear reflectors (2)

5) License plate light (1)

6a) Rear-side marker lights (2)

6b) Rear-side reflectors (2)

7a) Front-side marker lights (2)

7b) Front-side marker reflectors (2)

8) Rear identification lights

9a) Intermediate side marker lights (2)

9b) Intermediate side marker reflectors

Additional Lights for Trailers 80 Inches or Wider

1) Rear clearance lights (2)

2) Front clearance lights (2)

Exceptions:

Where to Mount Trailer Lights, Reflectors, and Conspicuity Treatments

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.

Tail lights*

Rear of trailer
Same height above the ground
Same distance from the trailer's vertical centerline
As far apart as possible

15 - 72 inches above the ground

Brake lights*

Rear of trailer
Same height above the ground
Same distance from the trailer's vertical centerline
As far apart as possible

15 - 72 inches above the ground

Turn signals

Rear of trailer
Same height above the ground
Same distance from the trailer's vertical centerline
As far apart as possible

15 - 83 inches above the ground

Rear reflectors*

Rear of trailer
Same height above the ground
Same distance from the trailer's vertical centerline
As far apart as possible

15 - 60 inches above the ground

License plate light

Rear of trailer
Above or to the side of license plate

Varies based on position of license plate

Rear side marker lights

One on each side of trailer
As far toward the rear of the trailer as possible

15 inches or more above the ground (On trailers 80 inches or wider, no more than 60 inches above the ground)

Rear side reflectors

One on each side of trailer
As far toward the rear of the trailer as possible

15 - 60 inches above the ground

Front side marker lights

One on each side of trailer
As far toward the front as possible
Not on trailer tongue

15 inches or higher above the ground

Front side reflectors

One on each side of trailer
As far toward the front as possible
Not on trailer tongue

15 - 60 inches above the ground

Intermediate side marker lights

One on each side of trailer
Halfway - or as close to halfway as possible - between the front and rear side reflectors

15 inches or higher above the ground

Intermediate side reflectors

One on each side of trailer
Halfway - or as close to halfway as possible - between the front and rear side reflectors

15 - 60 inches above the ground

Rear clearance lights

Rear of trailer
- May be located farther forward if necessary
Same height above the ground
Same distance from trailer's vertical centerline
As high as possible on trailer
- Can be lowered if identification lights are at the top or if header extends less than 1 inch above doors

N/A

Rear identification lights

Rear of trailer
Same height above the ground
Spaced 6 - 12 inches apart
As high as possible on trailer
- Can be lowered if header extends less than 1 inch above door

N/A

Front clearance lights

Front of trailer
- May be located farther rearward if necessary
Same height above the ground
Same distance from trailer's vertical centerline
As high as possible on trailer

N/A

*If only 1 light is used on a trailer less than 30 inches wide, it should be as close to the vertical centerline as possible

Rules That Apply to Trailer Lights and Reflectors

Trailer lights must be permanently mounted to the trailer.
Lights must be visible - they can't be blocked by another part of the trailer.
Lighting must be installed square to the trailer's centerline. For example, lights on the rear of the trailer must face toward the rear and not angle up, down, or sideways. PC combination side marker and clearance lights are an exception to this rule. To learn more about PC lights, see our section on PC vs. non-PC lights.

Proper Mounting Locations of Conspicuity Treatments

A pair of white reflective strips at each upper corner marks the rear upper body

Each pair consists of a horizontal and a vertical strip
Each strip must be 12 inches long
The strips must be mounted as close as possible to the upper and outer edges
Treatment can be mounted on the rear-facing surface of a bulkhead on an otherwise flat trailer
Treatment can be omitted on container chassis or platform trailers without bulkheads

N/A

A strip of alternating red and white tape (or reflectors) marks the rear bumper bar

Mounts along rear bumper or underride protection device
Runs the full width of bumper bar

N/A

A strip of alternating red and white tape (or reflectors) marks the rear lower body

Runs along full width of lower portion of body
Extends horizontally, as far as possible to each end

15 - 60 inches 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

Running along both sides of the trailer, as evenly spaced as possible
Covering at least 1/2 of trailer's length
Extending horizontally between the front and rear of the trailer as far as possible

15 - 60 inches 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 inches 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 inches 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
- Conspicuity treatment must be applied to a flat surface. It can't be applied over hinges, rivets, or corrugations.
Proximity of Conspicuity Tape to Lights
- The edge of any white marking tape must be at least 3 inches away from the edge of any required red or yellow light.
- The edge of any red marking tape must be at least 3 inches away from the edge of any required yellow light.
Splitting Marking Tape to Clear Rivets or Other Obstructions
- You can split DOT-C2 marking tape into (2) 1 inch wide strips, separated by a gap no bigger than 1 inch - to clear rivet heads or other small obstructions.
Red and White Marking Tape
- Each segment of red or white marking tape must be from 6 - 18 inches long.
  Shorter lengths can be used to clear obstructions.
  Longer lengths can be used to avoid placing white tape near red lights.
- In a continuous strip of alternating red and white, the total length of 1 color cannot be more than 2/3 of the total length of the strip.
  Example: If you apply tape in a 9 foot long section, the total length of red tape - when added together - cannot be greater than 6 feet because 6 feet is 2/3 of 9 feet.
Reflectors Used in Place of Tape
- Reflectors must be installed in a repetitive pattern of 2 or 3 white reflectors alternating with 2 or 3 red reflectors.
- The center of each reflector cannot be more than 4 inches from the center of each adjacent reflector.
- Additional reflectors are not required if the conspicuity material is placed at the locations of the required reflectors.

Trailer Lighting Standards (SAE Codes & DOT Regulations)

All trailer lights must be DOT compliant (you just know someone would try to duct tape a flashlight to the back of their trailer otherwise). This section is much more nitty-gritty than most trailer owners will ever need to get (if you're buying from a legit trailer supply company like etrailer, your lights should already be DOT compliant), but for the few who DO need it, let's talk about DOT requirements and SAE codes.

Fortunately, it's pretty easy to see if your trailer lights are DOT compliant, since the letters "DOT" will be listed right on the light, reflector, or tape. You'll also see a series of other numbers and letters, such as:

SAE - Indicates the lens was rated using standards developed by Society of Automotive Engineersedit
Codes for individual light functions (see chart for the key)
Year of manufacture
Manufacturer's identification number

As you can see, you can tell a lot about a trailer light by the series of letters and numbers printed on it. Below we'll include a chart with a breakdown of the most common SAE codes and their functions. Many lights can perform more than one function. As an example, the light pictured here has the code "ASTIP2," indicating that this light has the following functions: Rear, front, or side reflector; stop/brake lights; tail lights, rear turn signals, front or rear side marker or clearance lights.

When shopping for trailer lights, you might come across indicators like "PC rated" or "P2 rated". This simply refers to the range of visibility a light is able to cast. PC lights emit a beam that spreads out 90 degrees on each side, giving a total coverage of 180 degrees. This wide visibility makes them perfect for side markers as well as front and rear markers. On the other hand, P2/P3 lights emit beams that spread out 45 degrees on each side, totaling 90 degrees of coverage. While they're visible straight on, they're not clear from the sides of the trailer. Because of this, P2/P3 lights are better suited as front and rear markers.

PC-Rated vs Non-PC Rated Trailer Light Chart

Common Questions About Trailer Lighting

What does it mean when a trailer light is for trailers wider than 80 inches?

Trailers that are 80 inches (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 inch 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 inches 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 inches for this application, even though the trailer is wider than 80 inches. The rear clearance lights, though, could be designated for trailers that are 80 inches 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.

Adding a drain hole at the bottom of the light - The main idea behind this design is to let out water if it does get in. A short submersion won't necessarily damage the light. And because the hole is at the bottom of the light housing, the air that is trapped inside the light will help keep water away from electrical connections.
Sealing the light so that water can't get in - This kind of light is waterproof.

Written by: Amber S

Updated by: Jacob J

Last Updated: 5/13/2024

Mark

9/30/2025

I understand there are different requirements for different size trailers. I am confused about the actual difference in "marker lights" vs. "clearance lights". Trying to figure out what lights I want to buy, I see several lights can be used as either clearance or marker but not both. I'm looking for an explanation of the difference in the lights and how can ne light be used as either but not both. Is it about being PC rated or non-PC rated? If the light can be used as either or, is it a difference in mounting or wiring? Please explain. Mark Zieno

Jameson C.

9/30/2025

@Mark Clearance lights are ones that are located so that they indicate the overall height and width of a trailer. Marker lights on other hand are designed to help indicate the overall length of the trailer.

Pierre

6/4/2024

What color should a marker lamp be that is: Rear facing, but mounted on the back of the fender, five feet forward of the rear of the (type 2) trailer?

Andrew N.

6/4/2024

@Pierre Normally a fender would have a clearance light that faces both directions so that the widest point of the trailer can be seen from the front and rear. They vary in color but normally are either amber or red. You could use something like Optronics Thinline LED Trailer Fender Light w/ Bracket - Submersible - 10 Diodes - Amber/Red Lens # MCL67ARB. This is universal and has both colors and is visible from front or rear of the trailer's fender.

Mark

9/30/2025

@AndrewN I'm not sure you answered the question. Pierre said the light is mounted on the "rear" of the fender, which I assume is not the "top" of the fender. You gave an answer of either red or amber light or a combo. I think it's one or the other. If mounted on top, yes a combo amber/red would work. Maybe I misunderstood something.

Andrew N.

9/30/2025

@Mark Yeah it's hard to say exactly what Pierre was referring to without seeing photos, and every trailer is different. Really just depends.

Safecastle

5/24/2024

Seems like a useful resource for anyone who owns a trailer or is considering buying one. It's important to be aware of the trailer lighting regulations so that you can ensure your trailer is safe and legal to operate on the road.

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