A daytime running light is a forward-facing white lamp that switches on automatically when the engine starts, making the vehicle easier to see in daylight. Daytime running lights, shortened to DRLs, light the front of the vehicle only and do not illuminate the road. The lamps became mandatory on new car and van type approvals across the EU in 2011, which is why almost every vehicle built since then carries them. DRLs reduce daytime collisions by improving how early other road users spot an approaching vehicle. This guide covers what DRLs are, how they work, the night-time risk they create, the UK and EU law, and how to fit them to a farm vehicle.
What Daytime Running Lights Are
A daytime running light is a dedicated white front lamp designed to make a vehicle conspicuous in daylight. The DRL is not a headlamp and not a sidelight. The lamp produces a bright, fixed white light at the front of the vehicle, aimed to be seen by others rather than to light the road for the driver.
The purpose of a DRL is conspicuity, not illumination. A vehicle showing DRLs stands out against a grey road, a dark hedge, or a low winter sun, so other drivers, cyclists, and pedestrians register it sooner. Research behind the EU rule found that always-on front lighting cuts daytime multi-vehicle collisions, which is why the lamps became standard fitment.
The term DRL means daytime running light. The two names describe the same lamp. Vehicle handbooks, dashboards, and retailers use both freely.
A DRL differs from the three lamps drivers confuse it with. A DRL is brighter than a sidelight (position lamp) and points only forward. A DRL is far dimmer than a headlamp and does not light the road. A DRL is white and steady, unlike the flashing amber of an indicator.
For the wider auxiliary lighting picture, see Fog Lamps, DRLs, and Auxiliary Lights: What They Do and When You Need Them and Position Lamps: Front and Rear Sidelights Explained.
How Daytime Running Lights Work
Daytime running lights switch on automatically when the engine starts and switch off, or dim, when the driver turns on the headlamps. The DRL needs no action from the driver. The vehicle’s lighting control module powers the lamp the moment the ignition reaches the running position.
Three switching behaviours are common across vehicles built since 2011.
On with the engine. The DRL lights as soon as the engine runs, regardless of the light switch position, in daylight or dark.
Off or dimmed with the headlamps. When the driver selects the headlamps, the DRL either switches off or drops to a lower brightness, because the headlamp now performs the conspicuity job and a full-brightness DRL would add glare.
Off with the handbrake or indicator on one side. Some systems cut the DRL on the side where the indicator is flashing, so the amber signal is not washed out by the white DRL next to it.
The DRL draws its power from the engine-running circuit, not the light switch. The driver cannot leave a DRL on with the engine off, so a DRL never flattens the battery the way a forgotten sidelight can.
The single most important point about DRL behaviour is what it does not do. A DRL lights the front of the vehicle only. The lamp does not switch on the tail lights, the sidelights, or the headlamps. That gap creates the night-time risk covered below.
LED Daytime Running Lights: Technology and Power
LED daytime running lights use surface-mount LED chips to produce a bright white light at very low power draw. LEDs dominate DRL fitment because the technology suits the job. A DRL runs whenever the engine runs, so it must be efficient, long-lasting, and cool.
Three figures describe an LED DRL.
Power draw. An LED DRL draws 5 to 10 W per lamp. The low draw means the lamp adds almost nothing to the alternator load across a full working day, unlike a 21 W filament lamp run continuously.
Light output. A DRL produces 400 to 1,200 candela of white light, the range set by EU Regulation. The intensity is high enough to be seen in daylight but capped to avoid dazzling other road users.
Lifespan. LED DRLs last 30,000 to 50,000 hours, which exceeds the life of the vehicle in most cases. A filament DRL would need replacement several times over the same period because it runs every engine hour.
LED DRLs come in two forms. Form one, integrated DRLs built into the headlamp unit or a styled strip, fitted at the factory. Form two, separate aftermarket DRL modules, mounted in the bumper or grille and wired to switch with the ignition, used to retrofit an older vehicle or a tractor.
The white colour of an LED DRL sits between 5,000 K and 6,500 K, a cool white that reads clearly against daylight. The same colour temperature appears on LED work lamps and headlamp conversions.
For the LED technology behind these lamps, see What Are LED Work Lights and Why Are They Replacing Halogen and LED Headlamp Conversions: How to Upgrade from Halogen to LED.
The Night-Time Risk: DRLs Without Tail Lights
Daytime running lights create a night-time hazard because they light the front of the vehicle but leave the rear dark. The DRL switches on with the engine and stays bright, so the dashboard looks lit and the road ahead looks lit by the DRL glow. The driver assumes the lights are on. The tail lights, however, are not.
The risk plays out at dusk and at night. A driver pulls away with DRLs showing, sees light ahead, and never selects the headlamps. The front of the vehicle is visible to oncoming traffic from the DRLs. The rear of the vehicle shows no tail lights at all, so a following driver sees an unlit, dark shape until very close.
This fault is common enough that road safety bodies warn about it directly. The fix is simple but easy to forget: at dusk, the driver must select the headlamps, which brings in the tail lights, the sidelights, and the number plate light. A DRL is never a substitute for headlamps after dark.
Two design features reduce the risk on newer vehicles. Feature one, an automatic light sensor that switches the full lighting set on as the light fades. Feature two, a dashboard warning that prompts the driver when the headlamps are off in low light. Vehicles without these features, including many tractors and older vans, leave the decision entirely to the driver.
For agricultural operators, the lesson is direct. A tractor fitted with aftermarket DRLs must still have its full road lighting selected for any dusk or night road work, because the DRLs do nothing for the rear of the machine or the trailer behind it.
For the rear lighting that must come on at night, see Tractor Tail Lights and Rear Lighting: What the Law Requires and Position Lamps: Front and Rear Sidelights Explained.
UK and EU Law on Daytime Running Lights
UK law requires DRLs as standard fitment on new car and van type approvals but does not require a driver to retrofit them to an older vehicle. The rule came from EU Regulation, which mandated DRLs on new passenger car and small van type approvals from 7 February 2011, and on new trucks and buses from August 2012. The UK retained the requirement, so every car or van first approved since those dates carries DRLs from the factory.
Four points define the legal position in 2026.
DRLs are mandatory on new type approvals, not on existing vehicles. A vehicle built before 2011 is not required to have DRLs and does not need them fitted.
A retrofit DRL must meet the standard to be road-legal. An aftermarket DRL kit must carry an E-mark to ECE Regulation 87, wire to switch off or dim with the headlamps, and mount within the permitted height and position. A non-approved kit can fail an MOT.
A DRL must not be wired to stay on with the headlamps at full brightness. The lamp must dim or extinguish when the headlamps are selected, to avoid dazzle.
A DRL does not replace any other lamp. The law still requires headlamps, sidelights, and tail lights for night and poor-visibility driving. DRLs sit on top of that requirement, not instead of it.
For the dedicated regulatory article on DRL rules for cars, vans, and farm vehicles, see Daytime Running Lights: UK Rules for Cars, Vans, and Farm Vehicles. For the minimum legal lighting on a tractor, see Tractor Road Legal Lights: The Minimum Lighting Kit for UK Roads.
Fitting and Retrofitting Daytime Running Lights
Fitting a retrofit DRL kit takes 60 to 120 minutes and follows a fixed wiring sequence. The retrofit suits older vehicles, tractors, and pickups that left the factory without DRLs. The job needs a kit with the correct approval, a switched live feed, and a tidy mounting position.
The fitting sequence runs in 6 steps.
Step one, choose an E-marked DRL kit to ECE R87. The mark on the lamp confirms road approval.
Step two, mount the lamps in the grille or lower bumper, between 250 mm and 1,500 mm above the ground, at least 600 mm apart, and symmetrical about the centreline.
Step three, take a switched live from the ignition circuit, so the DRLs power up only when the engine runs.
Step four, wire the dimming or cut-off trigger to the headlamp feed, so the DRLs drop out when the headlamps come on.
Step five, fit an inline fuse on the supply, rated to the kit’s draw.
Step six, test in daylight and at dusk, checking the DRLs light with the engine and switch off or dim with the headlamps.
A plug-and-play DRL module that includes the dimming control simplifies steps three and four. Many aftermarket kits ship with a control box that senses the headlamp feed and handles the switching automatically.
For the wiring fundamentals behind any auxiliary lamp fit, see How to Wire Tractor Lights with a Relay: Complete Guide and Fuses and Circuit Protection for Vehicle Lighting.
Daytime Running Lights on Tractors and Farm Vehicles
Daytime running lights are not legally required on agricultural tractors, but they add useful daytime conspicuity for machines that mix road and field work. A tractor on a rural road in daylight is a slow, wide obstacle that following drivers can misjudge. A pair of DRLs lifts the tractor’s daytime visibility in the same way they lift a car’s.
Three tractor situations make a DRL retrofit worthwhile.
Road haulage in daylight. A tractor and trailer moving between fields on public roads benefits from DRLs that mark the front of the unit to oncoming and following traffic.
Low winter sun and dull days. A DRL stands out when a low sun flattens contrast and a dark tractor blends into a hedge line, which is common across a Lincolnshire winter.
Mixed fleets with newer cars. Operators used to DRLs on the farm car often add them to older tractors and pickups for consistency across the fleet.
The retrofit position on a tractor is the front grille, the bonnet corners, or the cab front rail, wired to the ignition through a relay and an inline fuse. The DRL must still dim or switch off when the tractor’s headlamps come on, and the operator must always select the full road lighting for any dusk or night work, because the DRL does nothing for the rear of the machine.
For the full tractor lighting picture, see The Complete Guide to Tractor Lighting and Tractor Lighting Regulations UK: Everything You Need to Know for Road Use. For products, browse the auxiliary lamps category at agri-lighting.co.uk.
The summary picture for daytime running lights in 2026: DRLs improve daytime conspicuity, they switch on with the engine and dim with the headlamps, they light the front of the vehicle only, they are mandatory on new car and van type approvals but optional as a retrofit, and they never replace the headlamps and tail lights that the law still requires after dark.