Fleet & Auto Reference Library · Technical Reference

Marker & Clearance Lamps

Clearance, side marker and identification lamps show the size and outline of a truck or trailer at night. This sheet explains each function, its color and location, and how to match a replacement.

Ref FA-0017FMVSS 108SAE J592

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

These are the small lamps that outline a vehicle. Clearance lamps mark the overall width and height at the upper front and rear corners. Side marker lamps mark the length along the sides. Identification lamps are a group of three lamps on the vehicle center line, front and rear, that tell other drivers the vehicle is a wide one. SAE J592 covers the performance of these lamps, and FMVSS 108 sets where they go and what color they must be.

How to identify

Look at the location and color first. A lamp at the upper corner facing front or rear is a clearance lamp. A lamp on the side is a side marker, and on longer vehicles there are intermediate side markers near the middle. A row of three close-set lamps on the center line is the identification group. Many lamps serve two functions, such as a combination clearance and side marker lamp at a corner, which lights toward both the rear and the side. The lens shows "DOT" and SAE function codes.

Function, color and location

Function	Color	Location
Front clearance	Amber	Upper front corners, vehicles 80 in or more wide
Rear clearance	Red	Upper rear corners, vehicles 80 in or more wide
Front side marker	Amber	Sides, near the front
Rear side marker	Red	Sides, near the rear
Intermediate side marker	Amber	Sides, near the middle of longer vehicles
Front identification (3 lamps)	Amber	Front center line, high as practical, on power units 80 in or more wide
Rear identification (3 lamps)	Red	Rear center line, high as practical, vehicles 80 in or more wide
Combination clearance/side marker	Amber front, red rear	Corners, visible to front or rear and to the side

Key points

Clearance and identification lamps are required only on vehicles 80 in (2032 mm) or more wide. Side marker lamps are required on trucks and trailers of all widths.
Identification lamps must be evenly spaced in a horizontal row. The spacing limits are in FMVSS 108.
Match the replacement by function, color, mounting style (flush, surface, grommet, bracket) and connection (pigtail, two-prong plug, PL-10 style and so on).
Grommet-mount lamps need the matching grommet and plug. Ordering by lamp diameter alone often misses them.
A combination lamp must be marked for each function it serves.

Common mistakes

Swapping an amber lamp onto the rear or a red lamp onto the front.
Replacing a combination corner lamp with a single-function lamp.
Leaving out one of the three identification lamps.
Ignoring the side reflex reflector requirement when replacing a lamp that had one built in.

Governing standards: FMVSS 108 (49 CFR 571.108); SAE J592 (clearance, side marker and identification lamps); 49 CFR 393.11.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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