What are daytime running lights (DRL)? Benefits and fleet safety

Daytime running lights or DRLs are low-intensity lights that automatically switch on when the engine is running, improving vehicle visibility on the road.

While some research shows daytime running lights could improve road safety, reducing everything from pedestrian accidents to head-on collisions, they are not currently mandatory in the U.S. This article will look at what DRLs are, how they differ from regular headlights, their benefits, where they are mandated and how they impact fleet safety.

What is the point of daytime running lights?

Daytime running lights’ primary purpose is to make vehicles easier to see during daylight hours, not to light up the road ahead. Unlike regular headlights, DRLs are designed to increase a vehicle’s visibility to other road users by creating more contrast with the surrounding environment. They turn on automatically when a vehicle’s engine starts.

Because they’re always on when the vehicle is running, daytime running lights are sometimes mistaken for headlights. However, they are usually smaller and dimmer than standard low beams and do not provide the same level of roadway illumination. Many newer vehicles use energy-efficient LED daytime running lights, while some older models rely on lower-wattage versions of their regular low-beam bulbs.

When should you use daytime running lights?

Because daytime running lights activate automatically whenever the vehicle is running, drivers do not typically "use" them the way they use headlights. They do not need to be turned on or off. They are intended to operate during all daylight conditions, including overcast or cloudy weather, dawn or dusk, bright sun that reduces contrast between vehicles and the road, light rain or snow.

Can you turn daytime running lights on or off?

In most vehicles, daytime running lights cannot be manually controlled and remain on whenever the engine is running. However:

• Some manufacturers include an off function accessible through a physical switch or infotainment menu.
• Even when possible, DRLs may automatically re-enable when driving or shifting out of "park" as a safety requirement.
• Turning on low-beam headlights, high beams or automatic headlights typically overrides daytime running lights.

Fleet managers should refer to vehicle manuals to understand whether DRL deactivation is capable.

DRLs vs. headlights vs. fog lamps

Although they all improve visibility, daytime running lights, headlights and fog lamps serve different purposes. 

• DRLs: These low-intensity, front-facing lights turn on automatically with the engine to make vehicles more noticeable during the day. Because they don’t illuminate the road or activate rear lights, drivers still need to switch on headlights in low-visibility conditions.
• Headlights: These provide full roadway illumination for nighttime or poor weather. They may activate automatically or manually and include both low beams for standard driving and high beams for dark, open roads.
• Fog lamps: These lights are designed for severe visibility issues like fog, snow or blowing dust. Their low, wide beam cuts through reflective moisture but isn’t a replacement for headlights in normal conditions.

Understanding the daytime running lights symbol

Most modern vehicles include a dashboard indicator to confirm the daytime running lights are active. Typically, this looks like a green sun or lamp icon with downward lines. The DRL light on the dash may change to indicate a problem:

• Solid green symbol: This is the normal state. Your DRLs are functioning properly.
• Amber light: This usually indicates a system malfunction or a burnt-out bulb.
• Flashing light: This can signal an electrical fault or a relay issue that needs immediate maintenance to avoid a safety violation.

Do certain states mandate daytime running lights? 

In most of Europe and Canada, DRLs are mandatory, but in the United States, they are considered optional. The Federal Motor Carrier Safety Administration allows daytime running lights on passenger cars, trucks and buses. They are "permitted but not required."¹

Additionally, no U.S. states currently mandate the use of DRLs, however, several states have specific rules about standard headlight usage during the day, especially in conditions that impact visibility. State laws vary, but most require drivers to turn on their headlights in certain conditions. Many states have a "wipers on, headlights on" rule of thumb, but there are more specific situations in the table below.

It is important for drivers to still turn headlights on in these conditions, because daytime running lights are not as bright as standard lights and, importantly, they do not activate your taillights. Rear lights are a critical safety warning for other drivers. Failing to activate your lights when visibility is low could trigger a citation or even cause a rear-end collision.

State Visibility Threshold

The rise of "daytime headlight required" zones

While daytime running lights are optional, many states are moving toward mandatory full headlight usage on specific stretches of road to reduce head-on collisions.

For example, the Nevada Department of Transportation is currently phasing in a major law² that will require all drivers to have their full headlights on while traveling on rural two-lane highways, with a total mandate effective July 1, 2028. Large signs reading "Turn on Headlights" are already being installed along major routes like U.S. 6 and U.S. 95. Enacted in 2019 in California, a daytime headlight section that stretches over a 39-mile section of Highway 99 has been successful enough that it prompted other highways to do the same.³

In these zones, daytime running lights are usually not enough. Because DRLs typically do not activate the vehicle's tail lights, they do not provide the 360-degree visibility required by these specific safety statutes. Fleet managers should train drivers to manually switch to standard headlights whenever they see "headlight zone" signage to avoid citations and improve safety on especially problematic roads.

Benefits of daytime running lights

The main advantage of daytime running lights is simple: they make fleet vehicles easier to see. Increased daytime visibility helps other road users detect approaching or turning vehicles sooner, especially in glare, cloud cover or other low-contrast conditions. For those researching what are daytime running lights and why they matter, the benefits fall into several categories:

• Improved visibility: Daytime running lights increase a vehicle’s contrast against the roadway, helping drivers judge distance and speed more accurately. This is especially useful for fleet vehicles that blend easily into busy or low-light daytime environments.
• Reduced crash risk: Studies show that DRLs reduce accidents in certain situations. According to the National Highway Traffic Safety Administration (NHTSA), daytime running lights reduce opposite-direction daytime fatal and non-fatal crashes by 5%.⁴
• Protection for vulnerable road users: The same study showed daytime running lights reduced pedestrian and cyclist fatalities in single-vehicle crashes by a substantial 12%. The most significant benefit of daytime running lights is for motorcyclists: DRLs reduced the likelihood of opposite-direction fatal collisions involving a passenger vehicle and a motorcycle by 23%.
• Operational advantages for fleets: LED daytime running lights use minimal power, require little maintenance and operate automatically, making them a low-effort, high-value safety enhancement across large fleets. LED lights in particular offer less battery drain and need replacement less often than a halogen light. Daytime headlight use reduced daytime crashes from light trucks and vans by 5.7%, a separate NHTSA study found.⁵
• Preparing for future potential regulations: Although DRLs are not required in the United States today, they are mandated in many countries, and increasingly common on new vehicles. As global standards continue to influence domestic manufacturing, daytime running lights may become a more widely expected safety feature in the years ahead, so forward-looking managers could prepare for future compliance.

Despite these benefits, it should be noted that in other types of crashes besides these listed, the studies found no significant benefit from daytime running lights.

See how fleet management software is already helping fleet safety programs, reducing accident costs and improving maintenance.

Other ways fleets can boost fleet safety

Because there is evidence that daytime running lights can help reduce crashes, fleet managers may look to include them as safety features when purchasing fleet vehicles. However, because they are not federally mandated, DRLs are not always a standard vehicle feature. They may be added after-market with the help of a qualified professional.

Fleet managers looking for other ways to help boost fleet safety may want to consider a fleet management solution that empowers them to develop and maintain effective safety programs. Fleet management can help impact safety in several ways:

• GPS tracking offers fleet managers greater insight into driver behaviors like speeding, harsh braking and sudden acceleration.
• Dashcam video can create greater awareness for drivers about their behavior through unsafe driving alerts, analysis and replayable video for personalized coaching.
• Maintenance programs with preventive maintenance analytics and diagnostic alerts help fleet managers catch issues before they lead to breakdowns.

Companies using fleet management software saw reductions in accident costs and insurance costs, underscoring how this technology can help fleets drive a safer tomorrow. To learn more, book a demo with one of our specialists.

Sources

¹ https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-571/subpart-B/section-571.108

² https://www.leg.state.nv.us/nrs/nrs-484d.html

³ https://dot.ca.gov/caltrans-near-me/district-3/d3-news/d3-news-release-20-239

⁴ https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/809760

⁵ https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811029