Pennsylvania Auxiliary Light Laws: Inspection, Limits, and Penalties

Pennsylvania’s auxiliary light laws allow passenger vehicles to run one pair of fog lamps and one pair of auxiliary driving lamps, provided they meet the mounting, aiming, color, and usage rules set out in Title 75 of the Pennsylvania Consolidated Statutes and Title 67 of the Pennsylvania Code. Off-road lights are allowed on the vehicle but cannot be used on public roads and must stay covered with an opaque cover. Violations carry fines up to $100 for equipment infractions, a flat $100 for using an off-road light on a highway, and $100 to $500 for lights that resemble those reserved for emergency vehicles.

Fog Lights

Fog lamps sit low on the front of a vehicle and cast a wide, flat beam designed to cut under fog, rain, or snow. You can install one pair on a passenger vehicle or light truck. The firm restriction: fog lamps cannot substitute for headlamps.¹ Running them with your low beams in bad weather is fine. Running them alone with your headlamps off is a violation.

Fog lamps must be front-mounted, spaced at least 20 inches apart center to center, and positioned no higher than 42 inches above the ground and no lower than the lowest chassis part of the vehicle. The beam must be aimed at or below the lamp’s horizontal centerline when measured at 25 feet with the vehicle pointed straight ahead.¹ Fog lamps also cannot be placed in front of any required lamp, so mounting them ahead of your turn signals or headlamps is not allowed.

Driving Lights

Auxiliary driving lamps extend your forward vision on dark roads by supplementing high beams. Pennsylvania allows one pair on a passenger vehicle or light truck, and they share the same mounting and aiming standards as fog lamps: at least 20 inches apart, no higher than 42 inches, no lower than the lowest chassis part, and aimed at or below the lamp’s horizontal centerline at 25 feet.¹

The critical difference is timing. Driving lamps may only operate with your high beams on, and they cannot substitute for headlamps.¹ When you dim for oncoming traffic, your driving lights need to go off too. Wiring them through the high-beam circuit so they cut out automatically is the simplest way to stay compliant.

One pair of each is the ceiling. You cannot stack multiple sets of aftermarket driving lights across your bumper and grille and expect them all to be legal.

Off-Road Lights and LED Light Bars

Roof-mounted light bars and bumper-mounted off-road floods are the easiest way to pick up a citation. Off-road lights on a roof or roll bar may not be used on any highway or trafficway, and they must be covered with an opaque covering at all times while the vehicle is on the road. Vehicles with these lights must also have a switch equipped with a pilot indicator light so the driver knows when they are on.¹

Turning on an off-road light while on a highway or trafficway is a summary offense carrying a flat $100 fine.² The opaque cover requirement is strict. If light can pass through it, the cover is not enough. A translucent or mesh cover will not satisfy an inspector. Snap-on vinyl covers or solid plastic shells are common solutions, and whichever you use must completely block the output.

A 50-inch LED bar bolted to a roof rack is legal on a trail. The moment you pull onto a public road, both the switch and the cover need to be in place. Forgetting to snap the covers back on after a weekend on the trails is one of the most common equipment citations officers write.

Mounting, Aiming, and Height Rules

Auxiliary driving lamps and fog lamps on passenger vehicles and light trucks must be front-mounted, spaced at least 20 inches apart center to center, and mounted no higher than 42 inches above the surface the vehicle stands on and no lower than the lowest chassis part.¹ For motorcycles and motorized pedalcycles, the mounting range is 12 to 42 inches.³

Aiming is where most DIY installations go wrong. No auxiliary driving lamp or fog lamp beam may project above the horizontal centerline of the lamp at 25 feet when the vehicle is pointed straight ahead.¹ Snowplow lamps have a tighter standard: the high-intensity portion of the beam cannot rise above 42 inches at 75 feet ahead of the vehicle. All lamps must be properly fastened and cannot obscure, change the color of, or block the beam of any required lamp.

Suspension changes matter here. If you lift your truck or install larger tires, the effective mounting height of every lamp changes. A light that was legal at 40 inches before a 3-inch lift is now at 43 inches and out of compliance. Re-aiming and possibly relocating your auxiliary lamps after any suspension modification is not optional.

Color and Intensity Limits

Forward-facing auxiliary lamps on a standard passenger vehicle should emit white or selective yellow light. Any lamp not specifically listed in the regulations and not located as described in the official equipment tables is prohibited unless it came as original equipment from the factory.¹

Red and blue forward-facing lights are off-limits for non-emergency vehicles. Using lights identical or similar to those reserved for emergency and authorized vehicles is a summary offense with fines between $100 and $500.⁴ That fine can apply even if you never actually turn the lights on in traffic; simply having them equipped on the vehicle can be enough for a citation.

On intensity, the combined candlepower of all headlamps and auxiliary lamps on a vehicle cannot exceed 150,000 total.¹ A pair of high-output LED driving lamps paired with modern LED headlights can approach that ceiling faster than you might expect. Rear lamps must also be lit whenever fog lamps or auxiliary driving lamps are in operation, so wiring auxiliary lights without a rear-lamp tie-in creates another inspection failure point.

Choosing Street-Legal Equipment

Not every auxiliary lamp sold online is legal for road use. The easiest way to tell is the DOT marking stamped into the lens. Under federal motor vehicle safety standard No. 108, headlamp lenses must carry a “DOT” symbol certifying compliance. For other lamps such as fog lights and driving lights, the DOT marking is optional but signals the manufacturer has certified the lamp meets federal requirements.⁵

Many aftermarket lamps marketed as “off-road only” deliberately omit DOT or SAE markings because they were not designed to meet beam-pattern or intensity standards for public roads. A lamp without either marking is almost certainly not intended for highway use, and installing it as your primary auxiliary driving lamp or fog lamp creates an immediate compliance problem at inspection. When shopping, look for the DOT stamp on the lens housing itself, not just on the box.

Passing Pennsylvania Safety Inspection

Pennsylvania requires an annual vehicle safety inspection, and auxiliary lighting is part of what inspectors check. Every lamp and switch on the vehicle must be in safe operating condition. If your vehicle has fog lamps or auxiliary driving lamps and one of them is broken, the vehicle fails inspection.⁶

The workaround most drivers do not know about: because fog lamps and auxiliary driving lamps are not required equipment, you can remove them entirely to pass rather than repair them.⁶ If one fog light in a pair burns out and you do not want to replace it, taking both assemblies off is a valid option. What you cannot do is leave a non-functioning auxiliary lamp mounted on the vehicle and expect to pass.

Inspectors also check that auxiliary lamps are properly aimed, securely mounted, displaying the correct color, and not blocking or altering any required lamp. Roof-mounted off-road lights must have their opaque covers in place. Any lamp not listed in the inspection tables and not factory-installed will be flagged as prohibited equipment.¹

Penalties for Violations

Pennsylvania’s auxiliary lighting penalties range from modest fix-it fines to serious ones for emergency-style lighting.

Selling, installing, or using vehicle equipment that does not comply with Pennsylvania’s vehicle code or applicable federal safety standards carries a civil penalty of up to $100 per violation.⁷
Illuminating an off-road lamp while on a highway or trafficway is a summary offense with a $100 fine.²
Equipping or using lights identical or similar to those reserved for emergency and authorized vehicles carries a fine of $100 to $500.⁴
If improper auxiliary lighting creates a genuine safety hazard, an officer can add a careless driving charge, a separate summary offense. Blinding an oncoming driver with poorly aimed auxiliary lamps is the scenario where this comes up most.⁸

Officers can stop you for an equipment concern whenever they have reasonable suspicion of a vehicle code violation, or during a systematic vehicle-check program.⁹ Uncovered off-road light bars and colored forward-facing lights are the most visible triggers because they are easy to spot from a distance.

Vehicles That Play by Different Rules

The rules above apply to standard passenger vehicles and light trucks. Some categories of vehicles operate under separate lighting authorizations, and it is worth knowing where those lines fall so you do not assume a rule you saw on someone else’s truck applies to yours.

Emergency Vehicles

Every emergency vehicle in Pennsylvania must be equipped with one or more revolving or flashing red lights and an audible warning system.¹⁰ Police vehicles, ambulances, and fire trucks operate under separate lighting rules allowing red, blue, and white flashing lights as part of their emergency signaling systems. Volunteer firefighters and ambulance personnel may equip personal vehicles with flashing blue lights under a separate authorization in the vehicle code.⁴ These lights require proper authorization and cannot simply be bought and installed at will.

Service and Construction Vehicles

Tow trucks, snow-removal equipment, highway construction and maintenance vehicles, and vehicles designated by PennDOT or the Pennsylvania State Police may use one or more flashing or revolving yellow lights.⁴ The intensity and manner of display are set by PennDOT regulation. Vehicles outside these categories cannot use yellow flashing or revolving lights, even for visibility on a work site.

1
Cornell Law School. 67 Pa. Code 175.66 – Lighting and Electrical Systems
2
Pennsylvania General Assembly. Pennsylvania Code Title 75 – Section 4303 General Lighting Requirements
3
Cornell Law School. 67 Pa. Code 175.175 – Lighting and Electrical Systems
4
Pennsylvania General Assembly. Pennsylvania Consolidated Statutes Title 75 Section 4572 – Visual Signals on Authorized Vehicles
5
eCFR. 49 CFR 571.108 – Standard No. 108 Lamps, Reflective Devices, and Associated Equipment
6
Pennsylvania Department of Transportation. PennDOT Safety Inspection Bulletin BI11-1
7
Pennsylvania General Assembly. Pennsylvania Code Title 75 – Section 4107 Unlawful Activities
8
Pennsylvania General Assembly. Pennsylvania Code Title 75 – Section 3714 Careless Driving
9
Pennsylvania General Assembly. Pennsylvania Code Title 75 – Section 6308 Investigation by Police Officers
10
Pennsylvania General Assembly. Pennsylvania Code Title 75 – Section 4571 Visual and Audible Signals on Emergency Vehicles