In the United Kingdom, what does a yellow box junction require drivers to do?

In the United Kingdom, a yellow box junction requires drivers to keep the exit clear before entering.

Yellow box markings are painted as a criss-cross grid, usually at junctions or other places where queuing traffic could block a crossing route. The basic rule is that a driver must not enter the box unless the exit road or lane is clear. This keeps the junction available for vehicles moving in other directions.

There is an important exception for a vehicle turning right. A driver may enter and wait in the box if the turn is blocked by oncoming traffic or by other vehicles waiting to turn right, provided the exit is otherwise clear. The markings regulate the road space, not simply whether the traffic signal is green.

Yellow box junctions are often confused with yellow lines, which control parking or waiting at the roadside. Their grid pattern and position across the carriageway identify their different purpose.