You must not enter a yellow box junction until your exit is clear. The single exception is a right turn where the only thing stopping you is oncoming traffic or other vehicles waiting to turn right. Everything else people believe about box junctions is either a misreading of that sentence or an invention.
Yellow criss-cross markings sit at hundreds of London junctions and the rule attached to them runs to two sentences. Drivers get it wrong in one of two directions.
Some treat the box as a place you may never stop under any circumstances, and sit back at the line when they were entitled to move. Others treat it as advisory paint to be ignored once the queue gets long. Neither reading survives contact with the wording.
The Rule, In Full
Two clauses. A prohibition carrying MUST NOT, which in the Highway Code means it is backed by law rather than offered as advice, and one narrow exception that applies to right turns only.
Everything difficult about box junctions comes from applying the second clause to situations it was never written for. It does not cover turning left. It does not cover going straight on.
It does not cover being held up by a pedestrian crossing, by a red light on the far side, or by a queue that has not moved. It covers oncoming traffic, and vehicles already waiting to turn right, and nothing else.
What "Exit Is Clear" Actually Means
It means there is enough room on the far side for the whole of your car, and that you can reach that room without stopping inside the markings. Not nearly enough room. Not room that will probably appear by the time you get there.
Transport for London states the same test from the other direction: "You may enter a yellow box junction when your exit is clear and there is enough space on the other side of the junction for your vehicle to clear the box completely without stopping." That is on TfL's page on yellow box junctions.
The word doing the work is "clear", in the present tense. You make the judgement at the moment you decide to move, on the evidence in front of you, not on a forecast.
If the car occupying the gap you are aiming for has not moved in fifteen seconds, that gap is not evidence of anything. Traffic that is flowing is different: a gap that is opening in front of you as you watch is a reasonable basis for going.
Two practical tests, in the order you should use them:
- Look past the box, not at it. Find the space your car will occupy when you have finished crossing, and check it exists now.
- Check that space is big enough for your car and not just for the front of it. A car length plus a little.
- Check nothing will take that space before you get to it, in particular a car turning in from the left ahead of you.
- If any of those three fails, hold at the line. Holding is never the fault.
The Right Turn Exception, And Its Limits
When you are turning right and the only obstacle is oncoming traffic, you may move into the box and wait. This is not a courtesy. It is how the junction is designed to work, because a car waiting inside the box can complete its turn on the amber, which is what keeps the right-turn queue from backing up into the through lanes.
Two things end the exception. The first is your exit. If the road you are turning into is itself blocked, the exception does not apply, because the exception permits you to wait for a gap in oncoming traffic, not to wait for a queue to clear.
The second is anything other than oncoming traffic. A pedestrian on a crossing at the mouth of the side road is not oncoming traffic. A red light on the road you are turning into is not oncoming traffic.
The most common misuse in London is a driver who has been sitting in the box for the whole of a phase, turning right into a road that has been full the entire time, and who believes the right-turn exception covers them because they are indicating right. It does not.
Why It Is Marked So Hard On Test
Box junctions sit inside the DVSA's marking category for response to road markings, which is seventh on the published list of reasons people fail.
The reason it gets marked at the severe end rather than as a routine driving fault is that a car stranded in a box is not a tidiness problem. It is a car sitting across the path of traffic that has a green light, which is exactly the situation the markings exist to prevent.
Examiners are not looking for a hesitant driver who never commits. Sitting at a wide open box while three phases go by collects marks of its own, under undue hesitancy. What they are looking for is a decision made on the right evidence.
The difference between the two on the report is the difference between a driving fault and a serious one, and one serious fault ends the test regardless of how clean everything else was. That distinction is set out in serious and dangerous faults explained.
Where They Cluster In East London
Box junctions follow congestion, so in these postcodes they follow the red routes and the main shopping streets.
| Where | What makes it awkward |
|---|---|
| A118 High Road, Ilford | Boxes at the side road mouths with a shopping street queue behind them, so the gap ahead moves in short bursts |
| Seven Kings | Station traffic and buses pulling out, which removes the space you were aiming for after you have committed |
| A13 side junctions | High approach speeds into a box, so the decision is made much earlier than it feels like it should be |
| A12 at Bow and Stratford | Multi-lane approaches where the lane beside you clears and yours does not |
| Mare Street and Barking Road | Bus stops immediately past the box, so the exit space is intermittently occupied |
Two of those matter for anyone testing at Goodmayes, because the A118 and Seven Kings are on the routes and the boxes there are the single most reliable source of marks at that centre.
The Situations That Trip People Up
The lane beside you clears
On a two-lane approach it is very easy to read the movement in the next lane as movement in yours. Your exit is your lane's exit. If the nearside lane is emptying and you are in the offside lane behind a stationary bus, nothing has changed for you.
The light goes green and you move on reflex
A green light is permission to proceed if the way is clear. It is not an instruction, and it does not override rule 174. The reflex to move on green is the single most common way a careful driver ends up stranded in a box.
Someone behind you is impatient
This is worth saying plainly, because it is the pressure that actually causes the offence. A driver behind you who wants you to go has no bearing on whether your exit is clear. Holding your position with a horn behind you is uncomfortable and correct.
Enforcement Away From The Test
In London, box junctions on the TfL road network are camera enforced, and TfL frames it as a traffic flow measure rather than a revenue one: "We don't simply issue PCNs to raise revenue, we enforce the rules to help keep the traffic moving." Boroughs enforce boxes on their own roads.
The penalty levels are set by regulation and change over time, so check the current position on TfL's penalty charge notice pages rather than trusting a figure you read on a forum.
What is worth knowing is that camera enforcement does not care why you stopped. It records that you entered and did not clear. If you were turning right and held up only by oncoming traffic, that is a ground for challenging a notice, and it is the reason it is worth being clear in your own mind which of the two situations you were in.
How To Practise It
Box junctions are one of the few things that cannot be usefully rehearsed on a quiet street, because the whole skill is reading traffic that is barely moving. The way to get good at them is to drive a route that has several in a row at a time of day when they are busy, and to say your decision out loud before you make it.
If you are already at test standard, they are worth putting on the list for a mock test, because the difference between a driver who reads a box well and one who is guessing shows up immediately when there is no commentary and no prompt.
The same reading skill carries over to two other London-specific rules that catch learners here: the timed lanes covered in London bus lanes explained, and the early lane choice covered in roundabout lane discipline.
All three are the same underlying habit, which is committing on evidence rather than on hope. The wider picture of what East London learners are up against is in the complete guide to learning to drive in East London.
Box junctions are one of the things that are much easier to learn in traffic with someone next to you than from a diagram, which is most of what an hour in an automatic on the A118 buys you.
Book automatic lessonsCommon questions about box junctions
Can I ever stop in a yellow box junction?
Yes, in one situation. Rule 174 allows you to enter the box and wait when you are turning right and are stopped only by oncoming traffic, or by other vehicles waiting to turn right. In every other case you must not enter until your exit is clear.
What if I enter a box and then the traffic ahead stops unexpectedly?
The rule is judged on the decision you made when you entered. If your exit was genuinely clear and something unforeseeable blocked it, that is different from entering on a gap that never existed. On test, an examiner watches the decision rather than the outcome, and the same reasoning is the basis for challenging a penalty notice.
Does the rule apply if the box is only partly marked or worn away?
The markings define the box, so if they are illegible the situation is arguable. It is not worth relying on. Faded paint is common on busy East London junctions and the safest approach is to treat any visible criss-cross as a live box.
Is a box junction fault automatically a test failure?
Not automatically, but it frequently is marked at the serious end, because a stranded car blocks traffic that has priority. One serious fault ends the test whatever else you did, so it is not a fault worth gambling on.
Are box junctions enforced by camera in East London?
On the TfL road network they are, and boroughs enforce boxes on their own roads. TfL publishes the current enforcement position and penalty details on its red route pages.
Do I need to worry about box junctions in an automatic?
The rule is identical. What changes is the failure mode: an automatic will creep forward on the brake alone, so drivers new to one sometimes ease into a box without deciding to. Keeping the footbrake on until you have chosen to go fixes it.
If box junctions are the thing you tense up about, an hour spent deliberately driving between them is worth more than an hour of general practice.
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Published 1 September 2026. Prices and DVSA figures are checked when this page is revised. If anything here has changed, ring us and we will confirm it.