What are daytime running lights?
Daytime running lights (also known as DRLs) are designed to make your vehicle more visible in bright, daytime conditions. These are low-energy lights that can be fitted to the front of a vehicle and help you to be seen by other road users, cyclists and pedestrians.
How DRLs work
- They should come on automatically when you start your engine
- DRLs are bright enough to be seen clearly in daylight but are too bright to be used at night when they would dazzle other road users
- They should go off automatically when you switch your headlights on (at night/when it's dark outside) or when you turn your engine off
- They don't have to be separate lights and are sometimes combined with the front position lamps (side lights). If this is the case, the DRLs dim when the headlights are turned on
- If your daytime running lights are very close to your indicators, the DRLs will turn off while the adjacent indicator flashes
A brief history on daytime running lights
- The Volvo 240 was the first car in Britain that could be said to have had DRLs – brighter bulbs alongside the standard sidelights were lit all the time unless the driver turned on the sidelights
- In the mid-80s the government launched plans for 'dim-dip' lighting – for use in urban areas at night – but these were scuppered when European standards couldn't be agreed; ‘dim-dip’ switched on headlights at reduced brightness when the ignition and side lights were on
- Much discussion followed about whether cars across Europe should have their headlights on all the time, and many countries introduced local rules
- By 2006, 12 countries had laws requiring headlights on all year round including:
- Sweden since 1977
- Iceland, Latvia, Macedonia and Norway since around 1980
- Denmark since 1990
- Romania, Slovenia and parts of Portugal since 1998
- Lithuania, Slovakia and the Czech Republic required daytime use of headlights in the winter only while Hungary and Italy required DRLs outside built-up areas
Daytime running lights UK law
So, are daytime running lights a legal requirement in this country? Since 2011, DRLs have been a legal requirement for all new passenger cars and small vans. Larger vehicles like buses, lorries and coaches are exempt from this rule, along with motorcycles.
DRLs are also not a valid substitute for headlights and shouldn’t be used in low-light conditions. You could get in trouble for having DRLs running at inappropriate times, as this could cause other drivers to be dazzled, leading to accidents.
Should daytime running lights always be on?
Daytime running lights should only be on while you’re driving during the daytime – the clue is in the name with this one! At night, daytime running lights should automatically turn off when you activate your headlights.
Do daytime running lights come on automatically?
In most modern vehicles, yes, the DRLs should come on automatically when you start driving during the daytime. Some modern cars also have sensors that can detect when the ambient light level is decreasing, which then leads to the headlights automatically turning on, while the DRLs automatically turn off.
Make sure to check your car’s manual for details about your daytime running lights.
Can you turn off your daytime running lights?
As daytime running lights are a safety feature, you can’t usually turn them off manually. However, some makes of car may feature a button that allows you to temporarily turn your DRLs off, which can be handy in certain situations (e.g. you’re driving through a tunnel and want to avoid dazzling any other drivers).
What controls daytime running lights?
Daytime running lights are typically controlled from the engine compartment or dashboard of a vehicle – the electrical system is stored there and features a DRL module, which (in modern vehicles) communicates with the vehicle’s sensors. As the ambient light level changes, the sensors send information to the DRL module, which causes the light to activate.
Why are my daytime running lights not working?
As there are a lot of technical parts involved in modern cars with DRL systems, there could be several reasons that they aren’t working, including:
- Broken/faulty sensor – The sensor that activates the lights could have an issue with it, you’ve checked all other possible causes and everything seems to be fine.
- Blown fuse – If the fuse for the DRL system is blown, then the lights won’t come on. If this is the cause, then you’ll need to replace the fuse.
- Faulty wiring – check the wires for any signs of damage or corrosion, again, this will need replacing if it’s the cause of the problem.
- Dead LED’s – the LED bulbs themselves may have simply ran their course and burnt out. You’ll need to either replace the bulbs or have the headlamp units checked by a mechanic.
- Faulty Headlamp module – the module may have suffered water ingress or have suffered another internal failure. This will need to be checked out using a diagnostic tool, or be removed and be visually inspected.
Fitting DRLs yourself
Thanks to European regulations, DRLs been fitted to most new cars and vans since 2011, and new trucks and buses since August 2012, but EU regulation applies to new cars only.
There’s no requirement to retrofit daytime running lights, but kits are available if you wish to do so. Look for an approval mark on the lamp which includes the letters 'RL'.
If you’re fitting daytime running lights they should be installed so that they come on with the engine and go off when headlights are turned on.
The benefits of daytime running lights
In 2006 the European Commission published research into the effectiveness, costs and benefits of introducing dedicated DRLs.
- Those in favour of DRLs claimed significant potential to reduce road deaths and serious injuries
- Those against objected to the constant glare of headlights and worried that motorcycle riders might become less conspicuous
- There was concern about increased fuel costs too
The Commission’s study suggested a lot of casualties could be prevented across the EU with a positive benefit-to-cost ratio, once the costs of fitting lamps and the environmental cost of running them was taken into account.
- A later UK (Department for Transport) study confirmed the Commission's findings on accident reduction but casts doubt about whether the benefit would outweigh the costs
- The UK study also found that dedicated DRLs could improve the visibility of cars in dim light without reducing the visibility of motorcyclists
Fuel consumption
The alternator (or electrical generator) is driven by the engine and spins all the time but it doesn't always consume the same amount of power from the engine. When the electrical load on the alternator increases, more power is required to turn it and your fuel consumption increases.
- Light Emitting Diodes (LED lights) only consume a fraction of the electricity taken by a normal headlight
Use of dedicated DRL instead of driving with headlights or sidelights also means that your tail lights and instrument lights aren’t on during the day
Last updated: 01 May 2024