What Are Running Lights on a Vehicle? | Auto-On Visibility Lights

If you’ve noticed your car’s front lights glowing while you drive during the day, those aren’t your headlights. They’re running lights, properly called daytime running lights (DRLs). Unlike headlights, which help you see the road, running lights exist so other drivers, cyclists, and pedestrians can see you in daylight, cloudy weather, or low light.

What Exactly Are Daytime Running Lights?

Daytime running lights are low-intensity, automatic lights mounted at the front of a vehicle, often built into the headlamp assembly or the front fascia. They switch on when the ignition starts or the vehicle shifts into gear, and they turn off or dim when you activate your main headlights or shut off the engine. Some manufacturers call them signature lights, but the function is the same: conspicuity, not illumination.

Their color is typically white. Geotab’s glossary notes that DRLs are designed to increase your vehicle’s visibility during daylight hours, and they do not light the road for you.

How Do Running Lights Behave in Practice?

DRLs operate automatically. The Mazda CX-9 owner’s manual, for example, states the running lights “turn on while the vehicle is being driven during the daytime” and will turn off when the parking brake is set or the gear selector is shifted into Park. It also notes they can be deactivated, usually through a vehicle setting.

Here are the uniform behaviors to expect:

• They come on automatically when you start the car or put it in gear.
• They go off when you turn on your headlights or switch off the engine.
• They light the front only. The RSA (Ireland’s road safety authority) says EU type-approval rules require DRLs only at the front, so most systems don’t illuminate the rear.

Are Running Lights Required in the U.S.?

No. While DRLs are common on most new passenger cars, SUVs, and light trucks sold in America, they aren’t federally mandated for all vehicles. Kelley Blue Book notes it’s not illegal to drive with a DRL burned out or missing because national law doesn’t require them.

This differs from Europe, where DRLs are tied to vehicle type-approval rules. The RSA confirms that under EU legislation, daytime running lights are a required component on new vehicle types, positioned at the front.

Because there’s no universal standard, behavior varies by make and model. Some vehicles use dedicated LED strips, while others integrate the function into the low-beam headlights at reduced brightness. Many vehicles offer no on-off switch at all, operating DRLs automatically with no driver control.

Common Mistakes to Avoid

Three misunderstandings cause most of the trouble around running lights:

• Confusing DRLs with headlights. DRLs help you be seen; headlights help you see. They are not interchangeable.
• Assuming rear lights come on. Most DRL systems don’t activate your taillights, which is why driving at night with only DRLs leaves you invisible from behind.
• Relying on them at night. DRLs are too dim or improperly aimed for night driving. You should not drive after dark with only running lights active.

If you’re unsure whether a vehicle’s DRLs can be disabled in a specific model, the manual is the only reliable source—Mazda’s documentation is a good example of a manufacturer-specific deactivation note.

Considering an Upgrade or Replacement?

If you’re looking for aftermarket options to replace worn units or add a modern look to an older vehicle, our tested roundup of quality vehicle running lights and kits covers the best options for common makes and models.