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Trailer Lighting Requirements

Light on PWD trailer lit up

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:





Determine Which Lights Your Trailer Needs

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

Diagram showing where to measure 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

Diagram showing where to measure 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.

Image of trailer label showing GVWR

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 for Trailers Less Than 80" Wide and Less Than 30' Long

Diagram with minimum required trailer lights

Required Lights
2 Stop/brake lightsThese 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 lightsThese functions are frequently combined into a single side marker light.
2 Front side marker reflectors

Exceptions

  • If your trailer is less than 6' long, you do not need to have front side marker lights or front side marker reflectors.
  • If your trailer is less than 30" 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.




Required Lights for Trailers 80" or Wider, Less Than 30' Long, and with a GVWR of 10,000 lbs or Less

Diagram of trailer over 80 inches wide illustrating required
lights

Required Lights
2 Stop/brake lightsThese 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 lightsThese functions are frequently combined into a single side marker light.
2 Front side marker reflectors
2 Rear clearance lightsFront and rear clearance lights can be combined on boat trailers.
2 Front clearance lights
Rear identification lightsID lights are often grouped into a single light bar.

Exceptions

  • If your trailer is less than 6' long, you don't need to have front side marker lights or front side marker reflectors.
  • US regulations state that 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 80" or Wider, Less Than 30' Long, and with a GVWR Greater Than 10,000 lbs

Diagram of trailer over 80 inches wide and greater than 10,000 lbs GVWR and less than 30feet long


Required Lights
2 Stop/brake lightsThese 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 lightsThese functions are frequently combined into a single side marker light.
2 Front side marker reflectors
2 Rear clearance lightsFront and rear clearance lights can be combined on boat trailers.
2 Front clearance lights
Rear identification lightsID lights are often grouped into a single light bar.

Exceptions

  • US regulations state that 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 Conspicuity Treatments for Trailers 80" or Wider, Less Than 30' Long, and with a GVWR Greater Than 10,000 lbs

Trailers 80" or Wider and over 10,000 lbs GVWR must have the following markings, which can consist of reflectors or reflective tape


Diagram of trailer over 80 inches wide and greater than 10,000 lbs GVWR illustrating required conspicuity treatments


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 for Trailers 30' or Longer (Regardless of Width or GVWR)

Diagram of trailer over 80 inches wide and greater than 10,000 lbs GVWR illustrating required lights and reflectors


Required Lights
2 Stop/brake lightsThese 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 lightsThese functions are frequently combined into a single side marker light.
2 Front side marker reflectors
Rear identification lightsID lights are often grouped into a single light bar.
2 Intermediate side marker lightsThese 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 lightsFront and rear clearance lights can be combined on boat trailers.
2 Front clearance lights

Exceptions

  • US regulations state that 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 Conspicuity Treatments for Trailers 80" or Wider, 30' or Longer, and with a GVWR Greater Than 10,000 lbs

Trailers 80" or Wider and over 10,000 lbs GVWR must have the following markings, which can consist of reflectors or reflective tape.


Diagram of trailer over 80 inches wide and greater than 10,000 lbs GVWR illustrating required conspicuity treatments

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.





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.


Proper Mounting Locations of Trailer Lighting

Light Location Position
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" 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" above the ground
Rear 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" 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" 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" or more above the ground (On trailers 80" or wider, no more than 60" above the ground)
Rear side reflectors
  • One on each side of trailer
  • As far toward rear of trailer as possible
15" - 60" 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" 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" 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" or higher above the ground
Intermediate side reflectors
  • One on each side of trailer as close to halfway between the front and rear side reflectors as possible
15" - 60" 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" above doors
N/A
Rear identification lights
  • Rear of trailer
  • Same height above the ground
  • Spaced 6" to 12" apart
  • As high as possible on trailer
    • Can be lowered if header extends less than 1" 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 the trailer's vertical centerline
  • As high as possible on trailer
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

  • 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

Conspicuity Treatment Location Position
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" 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" 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
  • 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" 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

  • 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" away from the edge of any required red or yellow light.
  • The edge of any red marking tape must be at least 3" 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" wide strips, separated by a gap no bigger than 1" - 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" to 18" 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' long section, the total length of red tape - when added together - cannot be greater than 6' because 6' is 2/3 of 9'.

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" 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

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

  • DOT - indicates that device meets US Department of Transportation requirements
  • SAE - shows that lens was rated using standards developed by Society of Automotive Engineers
  • Manufacturer's identification number
  • Year of manufacture
  • Codes for individual functions that device performs

SAE Codes on Trailer Light Lens

Trailer light cover and exploded view showing details of SAE codes

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.

  • A - Rear reflector
  • S - Stop light
  • T - Tail light
  • I - Turn signal
  • P2 - Rear side marker light

Trailer Lighting and Conspicuity Tape Codes

Function Color Code
Tail lightsRedT
Stop/brake lightsRedS
Rear turn signalsRed or amber (yellow)I
Rear reflectorsRedA
License plate lightWhiteL
Rear side marker lightsRedP2, PC, P3, or PC2
Rear side reflectorsRedA
Front side marker lightsAmber (yellow)P2, PC, P3, or PC2
Front side reflectorsAmber (yellow)A
Intermediate side marker lightsAmber (yellow)P2 or P3
Intermediate side reflectorsAmber (yellow)A
Rear clearance lightsRedP2, PC, P3, or PC2
Rear ID lightsRedP2 or P3
Front clearance lightsAmber (yellow)P2, PC, P3, or PC2
Rear upper body markersWhite
Bumper bar markersAlternating red and white
Rear lower body markersAlternating red and white
Side markersAlternating red and white





Common Questions About Trailer Lighting


What is the difference between lights that have a "C" in the code (PC and PC2) and those that don't (P2 and P3)?

Diagram to illustrate 45 degree light spread of P2- and P3-rated lights

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.



Diagram to illustrate 90 degree light spread of PC-rated lights

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

Trailer over 80" wide that can use combination
lights made for trailers 80" wide or wider

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

Trailer over 80" wide that wouldn't use
combination lights made for trailers 80" wide or wider

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.


Tall trailer over 80" wide that wouldn't use
combination lights made for trailers 80" wide or wider

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.


Back of trailer light housing to show water drain hole
  • 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.




James C.

2/15/2024

Do I need additional tail lights on a cargo basket that I have mounted to the back of my camper?

Etrailer Expert

Kevin C.

2/16/2024

@JamesC If the cargo carrier or the items in it are blocking the tail lights on the trailer then I would recommend installing some lights on the carrier, like Curt's # C53201, to remain street legal. These come with 3M adhesive strips on the back to easily attach them to the carrier and a 4-pole connector to connect with your RV. If your RV doesn't have a 4-pole connector then you can use the Curt # C47NR and splice into your tail light wiring for your light signals.

James C.

2/16/2024

@KevinC thank you Kevin! I have a generator going on there so it may need it done!

Youtube's ".

6/19/2023

We will be doing a short episode on resources available to help our viewer family be able to successfully wire their utility trailers. Our channel has almost 200,000 subscribers and we'd like to direct them to your website for resources as well as specific wiring diagrams for the more common 4 and 7-pin connection systems. If there a specific link or resource we can direct people to other than coming to your general website? Please advise!

Etrailer Expert

Mike L.

6/30/2023

@Youtube The page you'd looked at would be the best resource we offer regarding the legalities and regulations that apply to trailer lighting..

Jack S.

5/9/2023

"brake lights as far apart as possible" I have a 20' boat trailer about 60" wide: is it legal to mount the two brake lights 6" in from the edge of the frame, to protect them when turning the empty trailer in tight spots? This is almost as far as possible on this trailer, only 6" less (but as far apart as allows protecting the brake lights). thanks!

Etrailer Expert

Mike L.

5/10/2023

@JackS 6 inches in from the rear corners of the trailer will be fine. One thing you might not have considered is a protective housing that can sit around a 5-1/4" tall x 5-3/8" wide x 2-13/16" deep taillight like # CE26051A. These would allow you to install the lamps closer to the corners, and are compatible with taillights like # STL8RB and # STL9RB.

Bryan

3/17/2023

Trailer is over 80in wide and under 30 ft long. Can we make the front side markers into turn signals as well or add turn signals on side? So that cars directly beside the trailer can see the turn signal.

Etrailer Expert

Mike L.

3/24/2023

You can do this by using two of the # ST75AB lamp assemblies along with a # 118158 taillight converter. I'll link to a wiring diagram that will be helpful.

William

10/27/2023

@MikeL I remember years ago having the typical issue with turn signal flashers flashing rapidly due to the extra current load of additional lights introduced into the vehicles turn signal circuit. That's where you'd buy a heavy duty flasher. One time a trucker friend gave me a semi- truck flasher. It uses a small motor spinning a cam wheel that bumps a set of copper contacts causing lights to flash. With one of these you could have one or twenty lights flashing and always at same speed. If you're somewhat knowledgeable of electrical items like flashers, relays and lights you can get a two pole flasher from some luxury cars in the 70s-80's used them. Generally they are the three pin flashers rather than the standard two pin flasher. They were used on the front turn signals and the front side marker lights. When they flashed they alternated, one on the other off and vice-versa. It's actually a pretty cool setup to do. Power comes into the center pin and as the contact swings back and forth hitting the other two contacts it momentarily sends power the light on that circuit, then it let's go from that contact hitting the other contact powering the other light. Back and forth. Same circuit principle for cop cars with alternating emergency headlights. I think that would be cool on a trailer however, it would involve running a dedicated set of wires from tow vehicle to the trailer and going from simple 4 pin flat trailer plug to a 6 pin round connector plug. Of course being a custom set-up that would only work on trailers custom wired like that. As far as making the marker light flash with the trailer turn signal, just parallel connect it and disconnect the parking/marker light lead and connect it to another added marker light next to the existing one. If you can find a marker light that's brighter than the other, would be great. Then use the brighter ones for signals.

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?

Etrailer Expert

Mike L.

1/25/2023

You'll want to check with your local or state police regarding that.

William

1/28/2023

@EvanW its pretty much illegal to use any blue light on the highway. Blue lights are strictly for police, Sheriff, Border Patrol and Highway Patrol. Basically any arresting agency are the only ones allowed blue lights. Fire,ambulance are red. Construction- amber lights only.
Etrailer Expert

Mike L.

1/28/2023

Thanks for the info!
See All (8) Replies to Evan W. ∨


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