Clearance & Marker Lights - Incandescent

What Are Trailer Clearance and Marker Lights?

Clearance and marker lights are small but critically important lights mounted on the sides and front corners of trailers. Their primary job is to communicate a trailer's width and position to other drivers — especially in low-light conditions, bad weather, or at night. Federal Motor Vehicle Safety Standards (FMVSS 108) require these lights on trailers over a certain width, making them not just a safety upgrade, but a legal necessity for road use.

Incandescent clearance and marker lights remain a time-tested and cost-effective choice for trailer owners. Using traditional bulb technology, they are straightforward to wire, easy to replace, and widely compatible with existing trailer electrical systems. For trailers that don't require the longevity of LED technology — or for owners who simply need a reliable, budget-friendly replacement — incandescent units get the job done with a simple two-wire hookup and surface or stud-mount installation.

PC-Rated vs. P2-Rated: What's the Difference?

When shopping incandescent marker and clearance lights, you'll encounter two common ratings that describe how light is distributed:

• PC-Rated (Combination): These lights produce a 90-degree angle of light to each side for a total of 180 degrees of coverage. When mounted at a 45-degree angle, a single PC-rated light can function simultaneously as both a front or rear clearance light and a side marker light — a practical dual-purpose solution.
• P2-Rated: These lights are designed to serve as either a clearance light or a side marker light, depending on mounting position, but not both at the same time.

Understanding these ratings helps ensure your trailer meets DOT requirements while minimizing the number of lights you need to install.

Key Features to Look For

• Sealed or Waterproof Housing: Essential for boat trailers or trailers frequently exposed to rain and road spray. Look for sonically sealed lens-and-housing assemblies for maximum protection.
• Durable ABS or Polycarbonate Lens: Resists cracking and UV degradation better than standard plastics.
• Snap-On or Replaceable Lenses: Makes future maintenance fast and inexpensive — replace just the lens rather than the entire light assembly.
• Surface Mount vs. Stud Mount: Surface-mount lights use screws through mounting holes, while stud-mount designs use a single stainless steel stud for a cleaner, lower-profile installation.

Top Brands for Incandescent Clearance & Marker Lights

Optronics is one of the most recognized names in trailer lighting. Their incandescent marker and clearance lights — like the popular MC44 series — feature durable ABS housings, built-in reflex reflectors, and snap-on replacement lenses, making them easy to service in the field. Optronics offers both rectangular and round form factors in amber and red, with a simple two-wire design that suits a wide range of trailer applications.

Anderson Manufacturing has been producing safety lighting for the automotive aftermarket since 1945, and their incandescent marker lights are a staple of the trailer industry. Anderson lights are widely known for exceeding DOT specifications, and the Anderson Marine Division offers complete light kits with marker lights, harnesses, and hardware — everything needed to make a trailer street-legal in one package.

Wesbar has been building waterproof trailer lighting since 1934, with a particular focus on the demanding marine environment. Their incandescent clearance and marker lights feature sonically sealed, waterproof construction with break-resistant polycarbonate lenses and stainless steel mounting hardware — making them especially well-suited to boat trailers that regularly get submerged at the launch ramp.