Running lights on a truck are exterior lamps that make the vehicle visible to others, usually daytime running lights or the marker lamps that outline a truck’s width and position.
Whether you drive a pickup or a commercial rig, “running lights” can mean two different things depending on who you ask. The term gets used for the low-intensity front lights that switch on automatically, and it also gets used for the amber and red marker lamps that trace a truck’s outline. The distinction matters for one practical reason: they do different jobs, and neither one illuminates the road ahead.
Daytime Running Lights vs. Marker Lights
Daytime running lights (DRLs) are low-intensity front lights that turn on when the engine starts. They exist to make your truck more visible to other drivers, not to help you see. Marker lights, sometimes called clearance lights, sit on the front, sides, and rear to show a truck’s size and position — especially important on wide commercial vehicles and trailers.
The quick breakdown:
- DRLs: Front-facing, automatic, low intensity, for daytime conspicuity.
- Marker/clearance lights: Amber on the front and sides, red at the rear, outline the vehicle’s shape.
- Combined systems: Many trucks use both, and some marker lights double as turn signals.
Are Running Lights Required by Law?
U.S. federal rules do not treat “running lights” as a single lamp type, and daytime running lights are optional on trucks in the United States. Canada requires DRLs on new vehicles; the U.S. does not. That said, a truck-body industry summary notes that U.S. DRL lenses must be marked “DRL” if the device is not a headlamp, and they must be mounted symmetrically on the front with minimum separation from the ground.
Required lighting systems fall under Federal Motor Vehicle Safety Standard No. 108, which covers lamps, reflective devices, and associated equipment. That standard sets the location, height, and quantity rules for the lamps a truck must have. Marker and clearance lights on commercial vehicles are governed by these same federal rules through the FMVSS 108 lighting requirements.
What “DOT Approved” Actually Means
The National Highway Traffic Safety Administration (NHTSA) does not “approve” motor vehicle equipment, and it says “DOT/SAE approved” is not a meaningful claim for auxiliary lamps. Manufacturers self-certify that their lamps meet FMVSS 108, and compliant lenses carry a DOT marking plus an SAE code that may include a year mark. When you buy aftermarket lights, the certification language on the packaging is the manufacturer’s claim of compliance, not a federal endorsement.
If you add auxiliary driving or fog lamps, two rules matter: don’t install them where they block required lamps like turn signals, and never use them as substitutes for headlights. Mounting auxiliary lights where they reduce the effectiveness of required lighting is a compliance failure and a safety problem.
If you’re shopping for replacements or upgrades, the best truck running lights available now are covered in our tested roundup, which breaks down what actually fits and works on modern pickups.
Common Mistakes to Avoid
The biggest error is treating DRLs like headlights. They are for visibility, not roadway illumination, and they typically dim or switch off when you engage your headlamps. The second mistake is believing every “running light” is the same part — the term means DRLs, clearance lights, or marker lights depending on context. The third is trusting a “DOT approved” label on auxiliary lamps; that claim has no regulatory meaning.
For trucks and trailers, the lighting layout must match the vehicle’s width and length under FMVSS 108. Side and front markers run amber, rear markers run red, and each lamp position has specific requirements. A light certified for one position may not be legal in another, so check the SAE code on the lens before you install.
| Light Type | Color & Position | Primary Job |
|---|---|---|
| Daytime running lights | White/amber, front | Daytime visibility |
| Marker/clearance lights | Amber, front and sides | Outline width |
| Rear marker lights | Red, rear | Show position from behind |
| Turn signal markers | Amber, flashing | Combine position + signaling |
Running lights improve visibility, but they are not a substitute for headlights in darkness or bad weather. That distinction is what keeps drivers safe and compliant. The practical takeaway is simple: know which running lights your truck has, understand what each one does, and verify the markings on any aftermarket lamp before you bolt it on. Canada’s DRL requirements do not apply to U.S. vehicles, so don’t assume a Canadian-standard truck setup transfers automatically.
FAQs
Do daytime running lights drain the battery?
DRLs typically draw very little power, and most modern trucks manage them automatically with the electrical system. Leaving them on while the engine runs is normal, but if you’re parked with the ignition on for long periods, any exterior lamp can eventually strain a weak battery.
Can I drive with only running lights at night?
No. Running lights do not illuminate the road. DRLs and marker lights improve your visibility to others, but they lack the beam pattern needed for nighttime driving. Headlights must be on after dark or in low-visibility conditions.
Do all new trucks come with daytime running lights?
Most new light trucks sold in the U.S. include DRLs, but they are not federally required. Manufacturers add them because they improve safety and because Canada’s rules push many models to include them as standard equipment. If your truck lacks them, aftermarket DRL kits are available, but verify the markings before installing.
References & Sources
- NHTSA / Cornell Law. “49 CFR 571.108 — Lamps, reflective devices, and associated equipment.” Sets the federal lighting standard for U.S. vehicles.