Traffic lights at junctions in the theory test: what each signal means

At a junction controlled by traffic lights you must stop behind the white line unless the light is green. If the lights are not working, treat the junction as an unmarked junction and proceed with great care (rules 175 and 176).

This page sets out what each light means, how filter arrows and advanced stop lines work, and how to turn right at lights. Every rule is from the Highway Code on gov.uk. For the crossings that use similar signals, see our pedestrian crossings guide.

What each light means

The Highway Code section on light signals (gov.uk: light signals controlling traffic) gives these meanings:

Signal	Meaning
Red	Stop. Wait behind the stop line on the carriageway.
Red and amber	Stop. Do not pass through or start until green shows.
Green	You may go on if the way is clear. Take special care if you intend to turn left or right.
Amber	Stop at the stop line. Go on only if amber appears after you have crossed the line.
Green arrow	Movement in a certain direction is allowed, in addition to the full green signal.

Amber, red and the stop line (rules 175 and 176)

Rule 175 says you must stop behind the white line unless the light is green. On amber you may go on only if you have already crossed the stop line, or are so close that stopping might cause a collision.

Rule 176 says you must not move over the white line while the red light shows. On green, go forward only if there is room to clear the junction safely, or if you are turning right (gov.uk: rules 159 to 203).

Lights that are not working

Rule 176 says that if the traffic lights are not working, you should treat the situation as an unmarked junction and proceed with great care. That means looking for other traffic and giving way where you would at any junction without signs.

Green filter arrows (rule 177)

A green filter arrow indicates a filter lane only. Rule 177 says not to enter that lane unless you want to go in the direction of the arrow. It also says to give other traffic, especially cyclists, time and room to move into the correct lane.

Advanced stop lines (rule 178)

Rule 178 says motorists, including motorcyclists, must stop at the first white line reached if the lights are amber or red. If you crossed the first line when the signal changed to red, you must stop at the second white line.

The rule also tells you to allow cyclists, including any moving or waiting alongside you, enough time and space to move off when the green signal shows. Large vehicle drivers should stop well back from the first line so they can see the cyclists' waiting area.

Turning right at traffic lights (rules 179 and 180)

• Position (rule 179): check your mirrors, signal, and take up a position just left of the middle of the road, or in the space marked for traffic turning right.
• Making the turn (rule 180): wait until there is a safe gap between you and any oncoming vehicle, and do not cut the corner.
• Main road (rule 180): take great care when turning into a main road.

Practise the rules

The free practice questions let you try these rules in question form. Signal and sign shapes are covered in our road signs guide, and the test centres page lists centres by city if you are booking.

Check what you remember

Try the free theorytest.ai diagnostic to see whether traffic lights 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 traffic lights.

Frequently asked questions

What should you do at a junction controlled by traffic lights?

Stop behind the white line unless the light is green. On green, go on only if there is room to clear the junction (rules 175 and 176).

Can you go through on amber?

Only if amber appears after you have crossed the stop line, or stopping might cause a collision (rule 175).

What do you do if the traffic lights are not working?

Treat the junction as an unmarked junction and proceed with great care (rule 176).

Can you use a green filter arrow if you want to go straight on?

No. Rule 177 says not to enter the filter lane unless you want to go in the direction of the arrow.

Where do you stop at an advanced stop line?

At the first white line reached when the lights are amber or red. If you crossed it on red, stop at the second line (rule 178).