Sun glare, headlights and fog lights explained
Updated •6 min read
What can you do to reduce glare from bright sunlight? Slow down, and if necessary stop (Highway Code rule 93), and keep your windscreen clean.
If oncoming headlights dazzle you, slow down and stop if you need to (rule 115). Use dipped headlights at night in built-up areas and in dull daytime weather, and use fog lights only when visibility is seriously reduced (rules 113 to 116).
This page covers the legal lighting rules, when to use each type of light, and what to do about glare. Every rule is from the Highway Code on gov.uk, and each rule number links to our own rule page.
What the law says you must do (rule 113)
Rule 113 lists three things you MUST do:
- Keep all sidelights and rear registration plate lights lit between sunset and sunrise.
- Use headlights at night, except on a road with lit street lighting. These roads generally have a 30 mph limit, or 20 mph in Wales, unless signs show otherwise.
- Use headlights when visibility is seriously reduced.
The Highway Code defines night as the period from half an hour after sunset to half an hour before sunrise.
Which light to use when
| Light | When the Highway Code says to use it | Rule |
|---|---|---|
| Sidelights | Lit between sunset and sunrise | 113 |
| Dipped headlights | At night in built-up areas and in dull daytime weather, so you can be seen | 115 |
| Headlights | At night on roads without lit street lighting, and when visibility is seriously reduced | 113, 226 |
| Main beam (full beam) | When it would not dazzle others; keep dipped when overtaking until you are level with the other vehicle | 115 |
| Front or rear fog lights | Only when visibility is seriously reduced; switch off when it improves | 114, 226, 236 |
| Hazard warning lights | When stationary and temporarily obstructing traffic, or on a motorway or unrestricted dual carriageway to warn of a hazard ahead | 116 |
Full beam and dazzle (rules 114 and 115)
Rule 114 says you MUST NOT use any lights in a way that would dazzle or cause discomfort to other road users. That includes pedestrians, cyclists and horse riders.
Rule 115 says to keep your headlights dipped when overtaking until you are level with the other vehicle. Then change to main beam if necessary, unless this would dazzle oncoming road users.
The same rule says you should slow down, and if necessary stop, if oncoming headlights dazzle you. Rule 110 says only flash your headlights to let other road users know you are there.
In a stationary queue, rule 114 says to apply the parking brake and, once traffic behind has stopped, take your foot off the footbrake. That switches off your brake lights and cuts glare for drivers behind.
Fog lights (rules 226 and 236)
Rule 226 says you MUST use headlights when visibility is seriously reduced. The Highway Code says that is generally when you cannot see for more than 100 metres (328 feet).
You may also use front or rear fog lights then. Rule 236 says you MUST NOT use them unless visibility is seriously reduced, because they dazzle other road users and can hide your brake lights. You MUST switch them off when visibility improves (gov.uk: adverse weather rules).
Rule 235 adds that in fog you should beware of other drivers not using headlights. Our bad weather guide covers the rest of driving in fog, rain, ice and wind.
Glare from bright sunlight (rules 93 and 237)
Rule 93 says to slow down, and if necessary stop, if you are dazzled by bright sunlight. Rule 237 repeats this for hot weather (gov.uk: rules 89 to 102).
Two more points help with glare:
- A clean windscreen. Annex 6 says windscreens and windows MUST be kept clean and free from obstructions to vision. (gov.uk: Annex 6).
- Tinted glasses only by day. Rule 94 says not to use tinted glasses, lenses or visors at night or in poor visibility if they restrict your vision.
Annex 6 also says lights MUST be properly adjusted so they do not dazzle other road users, and must be kept clean.
Practice questions
These questions are written for this page to test the rules above. They are not DVSA questions.
- You are driving at dusk on an unlit country road and a car approaches with its lights on main beam. What should you do? Slow down, and stop if you need to, until you can see clearly (rule 115).
- When may you use rear fog lights? Only when visibility is seriously reduced, generally when you cannot see for more than 100 metres. Switch them off when it improves (rules 226 and 236).
- You are overtaking at night. When should you switch to main beam? Once you are level with the vehicle you are passing, and only if it will not dazzle oncoming road users (rule 115).
- Low sun is dazzling you on a bend. What should you do? Slow down, and if necessary stop (rule 93). A clean windscreen also reduces glare.
- Why should you not leave fog lights on when the fog clears? They dazzle other road users and can hide your brake lights (rule 236).
Practise the rules
Lighting questions also come up in the stopping distances guide for night and fog driving, and the Highway Code guide shows how the rules feed the test. Try the free practice questions to test yourself.
Check what you remember
Start free with the theorytest.ai diagnostic to see whether lights and visibility are a weak area. theorytest.ai is independent and is not affiliated with the DVSA. Gov.uk does not publish test questions, so we cannot say how many are about lights.
Frequently asked questions
What can you do to reduce glare from bright sunlight?
Slow down, and if necessary stop (rule 93). Keep the windscreen clean, as Annex 6 requires, and do not use tinted glasses at night or in poor visibility (rule 94).
What should you do if you are dazzled by bright sunlight?
Slow down, and if necessary stop (Highway Code rule 93). Keeping your windscreen clean also helps.
What should you do if oncoming headlights dazzle you?
Slow down, and if necessary stop (rule 115).
When should you use dipped headlights?
At night in built-up areas and in dull daytime weather, so that you can be seen (rule 115).
When can you use fog lights?
Only when visibility is seriously reduced, generally when you cannot see for more than 100 metres. You must switch them off when visibility improves (rules 226 and 236).
Do you have to use headlights on a street-lit road at night?
Not by law: rule 113 requires headlights at night except on roads with lit street lighting. Rule 115 still says to use dipped headlights at night in built-up areas.