Photo: Dominic Swain / Unsplash. Illustrative photograph.
In Great Britain, the Highway Code says you MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also switch on fog lights then, but you MUST NOT use them unless visibility is seriously reduced, and you MUST switch them off when it improves. This guide covers every light on your car under Rules 113 to 116, 226, 236 and 248 to 252.
Which light, when: quick table
| Light | Use it | Do not use it |
|---|---|---|
| Sidelights and rear number plate lights | MUST be lit between sunset and sunrise | As a substitute for headlights at night on unlit roads |
| Dipped headlights | At night in built-up areas; in dull daytime weather; MUST when visibility is seriously reduced | Never dazzle anyone |
| Full (main) beam | At night on unlit roads when it will not dazzle anyone | When it would dazzle oncoming drivers or other road users (Rules 114 and 115) |
| Front and rear fog lights | Only when visibility is seriously reduced, generally under 100 metres | MUST NOT use otherwise; MUST switch off when visibility improves |
| Hazard warning lights | When stationary, to warn you are temporarily obstructing traffic | MUST NOT use while driving, except on a motorway or unrestricted dual carriageway to warn of a hazard ahead |
The legal minimum at night (Rule 113)
You MUST:
- keep sidelights and rear registration plate lights lit between sunset and sunrise
- use headlights at night, except on roads with lit street lights (these generally have a 30 mph limit, or 20 mph in Wales, unless signs say otherwise)
- use headlights when visibility is seriously reduced
“Night” here means from half an hour after sunset to half an hour before sunrise.
Dipped headlights and full beam (Rules 114 and 115)
- You MUST NOT use any lights in a way that dazzles or causes discomfort to other road users, including pedestrians, cyclists and horse riders.
- Use dipped headlights at night in built-up areas and in dull daytime weather, so others can see you.
- Overtaking at night: keep dipped until you are level with the vehicle, then switch to full beam if needed, unless that would dazzle oncoming traffic.
- Dazzled by oncoming lights: slow down and, if necessary, stop. Look towards the left edge of your lane rather than into the lamps, and never answer with your own full beam.
- Queuing traffic: once the traffic behind has stopped, apply the parking brake and take your foot off the footbrake so your brake lights do not glare at the driver behind.
A lit dashboard does not prove your headlights and rear lights are on. Many cars light the instruments and run daytime running lights automatically, while the rear of the car stays dark. Learn the switch positions and warning symbols in your own car while parked, so you are not searching for them on the move.
More on judging this in the dark: driving at night as a learner.
When to use fog lights in the UK (Rules 226, 234 to 236)
- Visibility seriously reduced, generally when you cannot see for more than 100 metres: you MUST use headlights. You may add front or rear fog lights.
- Before entering fog: check your mirrors, then slow down.
- In fog: keep a safe distance and be able to stop well within the distance you can see clearly. Rear lights ahead can give a false sense of security. Watch for drivers not using headlights.
- Also in fog (Rule 235): use your wipers and demisters, and do not speed up to escape a driver who is too close behind. Check your mirrors before slowing, then brake so your brake lights warn following traffic. At a junction with limited visibility, stop in the correct position and listen for traffic; when you are sure it is safe, emerge positively rather than waiting in the path of approaching vehicles.
- When visibility improves: you MUST switch fog lights off. Rule 236 explains why: they dazzle other road users and can hide your brake lights.
Light rain or a dark evening is not a reason for fog lights. The test is whether visibility is seriously reduced. Weather in general: driving in rain, ice, fog, wind and heat.
Hazard warning lights while moving (Rule 116)
Hazard lights are for when you are stationary and temporarily obstructing traffic, for example after a breakdown. They do not make illegal or dangerous parking acceptable.
You MUST NOT use them while driving or being towed, with one exception: on a motorway or unrestricted dual carriageway you may use them briefly to warn drivers behind of a hazard or obstruction ahead. Use them only long enough for the warning to be seen. See what to do if your car breaks down.
Lights when parked at night (Rules 248 to 252)
- You MUST NOT park on a road at night facing against the traffic flow, unless in a recognised parking space.
- On a road or lay-by with a speed limit over 30 mph, all vehicles MUST show parking lights.
- On roads of 30 mph or less, cars may park without lights if they are at least 10 metres (32 feet) from a junction, close to the kerb and facing the direction of traffic, or in a recognised parking place or lay-by.
- In fog, avoid parking on the road. If you must, leave parking lights or sidelights on.
Full detail: parking at night and EV charging cables.
Lights on the driving test
Several vehicle safety questions on the practical test in Great Britain are about lights. “Tell me” questions include how you would check the headlights, tail lights and brake lights are working, how you would switch on the rear fog lights and when you would use them, and how you would switch from dipped to main beam and confirm main beam is on. One “show me” question asks you to switch on your dipped headlights while driving. Practise in the car you will use. See show me, tell me questions.
Common questions
Can I get in trouble for using fog lights when it is not foggy?
Rule 236 says you MUST NOT use front or rear fog lights unless visibility is seriously reduced. A MUST rule is a legal requirement.
What is the 100 metre rule for fog lights?
Rule 226 says you MUST use headlights when you generally cannot see for more than 100 metres. That is also when you may use fog lights.
Can I use hazard lights while driving?
Only on a motorway or unrestricted dual carriageway, briefly, to warn traffic behind of a hazard or obstruction ahead (Rule 116).
Do I need headlights on a lit street at night?
The legal duty to use headlights at night does not apply on roads with lit street lights, but Rule 115 says use dipped headlights at night in built-up areas.
Should I use dipped headlights in the day?
Yes, in dull daytime weather, so others can see you (Rule 115).
Can I use hazard lights to park on double yellow lines for a minute?
No. Rule 116 says never use them as an excuse for dangerous or illegal parking.
Back to the main guide: Learning to Drive in Great Britain. Related: signalling correctly, basic car maintenance.
Sources
- Department for Transport, “The Highway Code: General rules, techniques and advice for all drivers and riders (103 to 158)” (gov.uk)
- Department for Transport, “The Highway Code: Driving in adverse weather conditions (226 to 237)” (gov.uk)
- Department for Transport, “The Highway Code: Waiting and parking (238 to 252)” (gov.uk)