You may enter a box junction only when your exit road or lane is clear, meaning there is enough space for your vehicle to clear the box without stopping. The key exception is when you are turning right and are prevented from doing so by oncoming traffic or other vehicles also waiting to turn right; in this case, you may enter and wait in the box junction. The aim is to keep the junction clear and prevent blocking other traffic. If you are going straight or turning left, you must not enter unless you can clear the box junction completely without stopping.
Summary of When to Enter a Box Junction
- Enter only if your exit is clear and you can clear the box without stopping.
- If turning right, you may enter and wait if oncoming traffic or other right-turning vehicles block your path.
- Do not enter if your exit is blocked and you cannot clear the box.
- At signalled roundabouts with a box junction, you must be able to cross over without stopping.
These rules are designed to prevent gridlock and ensure smooth traffic flow at busy junctions.
