What Lights a Trailer Needs: Sealed LED vs Incandescent

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Trailer lights are how other drivers see you stop, turn and take up space on the road. The Optronics catalog's FMVSS Lighting Requirements chart for trailers groups the lamps and reflectors by what every trailer needs, then by width, length and weight. A utility trailer under 80 in. wide does not use the same set as a wide, long, heavy trailer.

This guide walks through that chart first: the lamps required on all trailers, then the extra clearance lamps, identification lamps and conspicuity tape that apply once a trailer is 80 in. or wider, 30 ft. or longer, or 10,000 lb. GVWR or more. After that it compares sealed LED and incandescent lamps, using Optronics catalog specifications unless another source is named. The chart is printed in Optronics' 2019 LED Truck and Trailer Lighting catalog; always confirm current federal and state rules for your trailer.

Key takeaways

Every trailer needs a basic set. The Optronics trailer chart lists tail lamps, stop lamps, rear turn signals, a license plate lamp, rear and front side marker lamps, and matching red and yellow reflex reflectors as basic equipment required on all trailers.
Width, length and weight add lamps. Trailers 30 ft. or longer also need intermediate side marker lamps and reflex reflectors. Trailers 80 in. or wider also need front and rear clearance lamps and three rear identification lamps. Trailers that are both 80 in. or wider and 10,000 lb. GVWR or more also need conspicuity tape.
Color tells you which end you are on. On the chart, rear tail, stop, side marker, clearance, identification and reflex devices are red (rear turn signals may be red or yellow). Front side markers, front side reflex reflectors and front clearance lamps are yellow.
A combination taillight can cover several functions in one housing. Optronics' universal combination tail lights, for example, combine stop, turn and tail, and the driver-side lamp can include a license illuminator. Some series also include side marker and reflex functions.
Sealed LED and incandescent differ in current draw, service and warranty. On a matched pair of universal combination lights, the LED version draws 0.259 amp on stop/turn versus 2.5 amp for the incandescent version. Optronics lists a lifetime limited warranty on its LED lighting products (connectors are covered for three years) and a three-year limited warranty on its incandescent 12-volt lighting products.

Terms used in this guide

Stop/turn/tail lamp: A rear lamp, or a combination lamp, that shows a tail light, a brighter stop light and a turn signal.
Marker/clearance lamp: A lamp that marks the trailer's length or width. The catalog chart treats side markers (required on all trailers) and clearance lamps (required on trailers 80 in. or wider) as separate functions.
Identification (ID) lamps: A row of exactly three red lamps on the rear of a trailer 80 in. or wider, used to indicate a wide vehicle.
License plate lamp: A white lamp that illuminates the license plate, mounted above or at the sides of the plate.
Reflex reflector: A reflector, not a lamp, that returns light toward its source so the trailer can be seen when lamps are not the only cue. The chart calls for red reflectors at the rear and rear sides, and yellow reflectors at the front sides (plus intermediate yellow reflectors on long trailers).
Combination taillight: One housing that combines several rear functions, often stop, turn and tail, and on many driver-side lamps a license illuminator.
Sealed LED: A lamp that uses diodes instead of a replaceable bulb. Many Optronics LED series are listed as sonically sealed and waterproof, with a lifetime LED warranty on the diodes.
Incandescent: A lamp that uses a replaceable bulb. Optronics incandescent 12-volt lighting products carry a three-year limited warranty. Many combination lights use a screw-on lens so the bulb can be changed, with a shock-proof socket "to guarantee long bulb life."
Conspicuity tape: Red/white retroreflective marking required on the Optronics chart when a trailer is 80 in. or wider and 10,000 lb. GVWR or more.
FMVSS/CMVSS 108: The federal (and Canadian) lighting standards the Optronics catalog cites. The catalog says every lamp, reflex reflector and conspicuity treatment must be permanently attached in the location specified and must comply with those standards where they apply.

Step 1: Start with the lamps every trailer needs

The Optronics catalog chart titled "Basic equipment required on all trailers" is the starting point, regardless of whether you choose sealed LED or incandescent lamps. Quantities below are the catalog's minimums (or an exact count where the chart says "exactly").

Function	Minimum quantity	Color	Location (catalog chart)	Height from the ground
Tail lamps	2	Red	On the rear, symmetrical, as far apart as practicable	15-72 in.
Stop lamps	2	Red	On the rear, symmetrical, as far apart as practicable	15-72 in.
Rear turn signal lamps	2	Red or yellow	On the rear, symmetrical, as far apart as practicable	15-83 in.
Rear reflex reflectors	2	Red	On the rear, symmetrical, as far apart as practicable, facing rearward	15-60 in.
License plate lamp	1	White	On the rear, above or at the sides of the license plate	No requirement
Rear side marker lamps	2	Red	Each side at the rear, as far back as practicable	15-60 in.; no maximum on trailers under 80 in. wide
Rear side reflex reflectors	2	Red	Each side at the rear, as far back as practicable, facing sideward	15-60 in.
Front side marker lamps	2	Yellow	Each side at the front, as far forward as practicable	15 in. minimum
Front side reflex reflectors	2	Yellow	Each side at the front, as far forward as practicable, facing sideward	15-60 in.

Table note: Locations and heights are from the Optronics FMVSS Lighting Requirements - Trailers chart. Heights are the catalog's inch figures (the chart also lists millimeters). The chart's important note says every lamp, reflex reflector and conspicuity treatment must be permanently attached in the location specified and must comply with FMVSS/CMVSS 108. The face of a front or rear device should be perpendicular to the vehicle's centerline, and the face of a side device should be parallel to it, unless the device is photometrically certified at its installation angle.

Stop, turn and tail are often built into one rear combination lamp. A license lamp may be built into the driver-side combination lamp or mounted as a separate license light or bracket. Side markers and reflex reflectors can be separate parts, or a marker lamp with a reflex lens, such as a red surface-mount LED marker/clearance light with reflex. Shop Stop/Turn/Tail LED Lights, Marker/Clearance LED Lights and Reflectors.

Step 2: Add lamps when the trailer is longer, wider or heavier

The same chart adds equipment once a trailer exceeds the measurements below. Measure overall width and length, and use the trailer's GVWR, before you order.

When this applies	Added equipment	Quantity and color	Location and height (catalog chart)
Length 30 ft. (9.1 m) or longer	Intermediate side marker lamps	Minimum 2, yellow	Each side near center, facing sideward; 15 in. minimum height
Length 30 ft. (9.1 m) or longer	Intermediate side reflex reflectors	Minimum 2, yellow	Each side near center, facing sideward; 15-60 in.
Width 80 in. (2032 mm) or wider	Rear clearance lamps	Minimum 2, red	At the widest point, symmetrical, on or near the rear, facing rearward; as high as practicable (may be lower only if the identification lamps are at the top). The chart states these "MAY NOT be combined with tail lamps."
Width 80 in. (2032 mm) or wider	Rear identification (ID) lamps	Exactly 3, red	On the rear, centered, spaced 6 in. to 12 in. apart, facing rearward; at the top (may be lower if the door header is narrower than 25 mm)
Width 80 in. (2032 mm) or wider	Front clearance lamps	Minimum 2, yellow	At the widest point, symmetrical, on or near the front, facing forward; as high as practicable
Width 80 in. or wider AND GVWR 10,000 lb. or more	Conspicuity treatment (red/white tape unless a listed option applies)	See the catalog chart for each area	Rear upper body (white corner strips at the top), bumper bar, rear lower body (full width), and each side (continuous or evenly spaced over at least 50% of the length, ending as close to the front and rear as practicable). Lower body and side tape should sit as close as practicable to 375-1525 mm (about 15-60 in.) from the ground.

Table note: From the same Optronics trailer chart. The chart also notes that reflex reflectors may not be required if they are replaced in their required location with conspicuity treatment, and that in Canada the rear lower body and side conspicuity may also be solid white, solid yellow, or white and yellow. A further note says the edge of red conspicuity tape shall not be closer than 75 mm to the edge of any amber lamp, and the edge of white conspicuity tape shall not be closer than 75 mm to the edge of any lamp.

Identification lamps are commonly sold as a three-lamp bar. The Optronics sealed LED identification light bar on a stainless steel base (MCL97 series) is cataloged "for over 80 in. applications." See Optronics Red Stainless Steel Sealed 3-Piece LED Identification Light Bar and all LED ID Light Bars. For the tape, see Conspicuity Tape.

The catalog also sells DOT-compliant back-up lights, but back-up lamps are not listed on the "basic equipment required on all trailers" chart. Add them if you want them, not because that chart requires them. See Back-Up LED Lights.

Step 3: Choose separate lamps, combination lights or a kit

You can build the chart's functions from separate stop/turn/tail, marker, license and reflector parts, or use combination lights and kits that group several functions.

On Optronics' incandescent universal-mount combination tail lights (ST8/9 series), the catalog says the passenger-side light is 6-function: stop, turn, tail, rear reflex, side marker and side reflex, and the driver-side light also includes a license illuminator. The LED counterparts (STL8/9 series) are described as a traditional style that "fits many applications," with the driver-side lamp including a 3-LED license light. For trailers under 80 in. wide, see the LED driver-side combination taillight with license light and the matching passenger-side lamp, or the incandescent universal under 80 in. combination taillight with license light.

For trailers 80 in. or wider, Optronics catalogs a separate combination series "designed for over 80 in. wide applications" (STL2/3 LED and ST2/3 incandescent). See the LED combination taillight for over 80 in. applications, driver side. Remember the chart's rule that rear clearance lamps may not be combined with tail lamps; if you use a combination taillight on a wide trailer, plan separate rear clearance lamps at the widest point and as high as practicable, plus the three-lamp identification bar.

Trailer light kits are a third path. Our Optronics LED and incandescent kits are listed by the same three thresholds the catalog chart uses: under or over 80 in. wide, under or over 30 ft. long, and under or over 10,000 lb. capacity. For example, the Extreme LED kit for under 80 in. wide, under 30 ft. long and under 10,000 lb. and the Extreme LED kit for over 80 in. wide, over 30 ft. long and over 10,000 lb. sit at opposite ends of that range. We also list one-diode LED kits in square, round and oval for single-axle trailers. Open a kit listing and confirm it matches your width, length and weight, and that the functions in the kit cover the chart for your trailer. Shop Optronics LED Kits and Optronics Incandescent Kits.

Step 4: Compare sealed LED and incandescent

Both families are sold as trailer lamps. The catalog differences that matter when you choose are construction, current draw, how you service a failed lamp and the warranty Optronics prints for each family.

	Sealed LED (Optronics catalog)	Incandescent (Optronics catalog)
How it makes light	Diodes inside a sealed housing. Many series are listed as "sonically sealed, waterproof."	A replaceable bulb. Many combination lights have a screw-on lens "easy to change bulbs" and a shock-proof socket "guarantees long bulb life." Some sealed incandescent series are also listed as sonically sealed and waterproof.
Current draw, matched combination example	STL8/9 LED universal combination: 12.8 VDC, 0.259 amp stop/turn, 0.062 amp marker	ST8/9 incandescent universal combination: 12.8 VDC, 2.5 amp stop/turn, 1.0 amp tail
Current draw, over 80 in. combination example	STL2/3 LED: 12.8 VDC, 0.268 amp stop/turn, 0.059 amp marker	ST2/3 incandescent: 12.8 VDC, 2.5 amp stop/turn, 1.0 amp tail
Warranty, as printed in the catalog	Optronics LED Lifetime Limited Warranty: LED lighting products are warranted for the lifetime of the original purchaser from defects in workmanship and/or materials. That limited lifetime coverage includes every diode in the unit. Connector failure is covered by a three-year limited warranty. It does not apply to severe applications such as construction or off-road use, and it does not cover damage from accident, misuse or abuse. The warranty is not transferable and applies to the original installation.	Incandescent 3-Year Limited Warranty: incandescent 12-volt lighting products are warranted for three years from defects in workmanship and/or materials only. The warranty is not transferable and applies to the original installation.

Table note: Amp draw is from the Optronics catalog pages for those series, not a general rating for every lamp we sell. Warranty language is summarized from the catalog's warranty page. If a product fails, follow the maker's replacement procedure; Optronics says to contact an authorized distributor or its customer service.

A sealed rectangular LED stop/turn/tail light such as the Optronics Rectangular LED Stop/Turn/Tail Light is typical of the LED grommet-mount style: a sonically sealed lamp (the catalog lists the STL34 version as the light plus grommet and plug). Incandescent sealed 4 in. round stop/turn/tail lights are listed the same way, with a three-year warranty and a shock-proof socket for the bulb.

LED lamps draw less current in the examples above, which can matter on a long harness or a tow vehicle with a lot of trailer lamps on the circuit. Incandescent lamps remain a straightforward choice when you want a screw-on lens and a replaceable bulb. Shop both families under Optronics LED Lights and Optronics Incandescent Lights.

Trailer lights ordering checklist

Overall trailer width: under or over 80 in.
Overall trailer length: under or over 30 ft.
GVWR: under or over 10,000 lb. (this decides whether conspicuity tape is on the catalog chart).
The basic set: stop, turn, tail, license lamp, front and rear side markers, and the matching reflex reflectors.
If 30 ft. or longer: intermediate side markers and intermediate side reflex reflectors.
If 80 in. or wider: front and rear clearance lamps, and a three-lamp red identification bar or equivalent. Do not combine rear clearance lamps with tail lamps.
If 80 in. or wider and 10,000 lb. GVWR or more: red/white conspicuity tape in the locations the chart shows.
Style: separate lamps, combination taillights (driver side often includes the license lamp; order the passenger side too), or a kit listed for your width, length and weight.
LED or incandescent, plus the grommets, plugs, brackets and trailer wire the mount requires.
Optional DOT-compliant back-up lamps, if you want them. They are not on the catalog's required-equipment list for trailers.

Frequently asked questions

What lights does every trailer need?

According to the Optronics trailer chart, the basic set is tail lamps, stop lamps, rear turn signals, a license plate lamp, rear and front side marker lamps, and red rear and rear-side reflex reflectors plus yellow front-side reflex reflectors. Quantities are at least two of each lamp or reflector, except the license plate lamp, which is a minimum of one.

When do I need clearance lamps and an identification light bar?

When the trailer is 80 in. or wider. The chart adds two red rear clearance lamps, two yellow front clearance lamps, and exactly three red identification lamps on the rear, centered and spaced 6 in. to 12 in. apart, at the top.

When is conspicuity tape required?

On the Optronics chart, when the trailer is 80 in. or wider and 10,000 lb. GVWR or more. The chart shows red/white marking on the rear upper corners, bumper bar, rear lower body and both sides.

What is a combination taillight?

A single housing that combines several rear functions. Optronics' universal combination tail lights combine stop, turn and tail, and the driver-side lamp can include a license illuminator. Some series also include side marker and reflex functions. Combination lights still have to be chosen for the trailer's width (under 80 in. or over 80 in. series), and rear clearance lamps on wide trailers may not be combined with tail lamps.

How do sealed LED and incandescent lamps differ?

LED lamps use diodes in a sealed housing; many Optronics LED series are sonically sealed and waterproof and carry the catalog's lifetime LED limited warranty on the diodes (three years on connectors). Incandescent lamps use a replaceable bulb and carry a three-year limited warranty. In the catalog's matched universal combination examples, the LED lamp draws 0.259 amp on stop/turn versus 2.5 amp for the incandescent lamp.

Does a trailer have to have back-up lights?

The Optronics FMVSS trailer chart does not list back-up lamps as required equipment. Optronics does catalog DOT-compliant back-up lights if you want them.

What color should marker and clearance lamps be?

On the chart, rear side markers, rear clearance lamps, rear identification lamps and rear reflex reflectors are red. Front side markers, front side reflex reflectors and front clearance lamps are yellow. Rear turn signals may be red or yellow.

How high should the lamps be mounted?

Use the catalog chart. Most rear lamps and reflectors fall in a 15-60 in. or 15-72 in. window from the ground (rear turn signals up to 83 in.). Front side markers have a 15 in. minimum. Clearance and identification lamps on wide trailers are mounted as high as practicable, with the identification lamps at the top unless the door header is narrower than 25 mm.

Will a trailer light kit cover everything?

Our Optronics kits are listed by width, length and capacity ranges that match the catalog chart's thresholds. Open the kit listing and confirm those three measurements, and that the functions in the kit cover the chart for your trailer, including license lamps, reflectors, clearance and identification lamps, and conspicuity tape when those apply.

References

Optronics International. LED Truck and Trailer Lighting catalog (ZH2019M, 2019): FMVSS Lighting Requirements - Trailers; sealed LED and incandescent stop/turn/tail, marker/clearance, license, identification, combination tail light, back-up and kit sections; LED Lifetime Limited Warranty and Incandescent 3-Year Limited Warranty.
Optronics International. LED Truck and Trailer Lighting catalog (ZH2019M, 2019): Truck and Trailer Regulation - FMVSS 108 conspicuity tape application.
Southwest Wheel product listings for Optronics lamps, Optronics LED and incandescent trailer light kits, and 3M Diamond Grade conspicuity tape (titles and functions as listed).