What is a yellow box junction and when can I enter it in Northern Ireland?

A yellow box junction is a keep-clear area; in general you must not enter unless your exit road or lane is clear.

The purpose is to prevent queuing vehicles from blocking the junction. There is an important exception for certain right turns when your exit is clear but you are prevented from turning by oncoming traffic or other right-turning vehicles.

For “What is a yellow box junction and when can I enter it in Northern Ireland?”, the wider Northern Ireland context is this: Northern Ireland's Highway Code uses signs, signals and road markings together, so the safest reading is always the exact sign at the location plus any lane arrows, plates or temporary traffic management. Rules expressed as ‘must’ or ‘must not’ are legal requirements; advisory wording can still be used as evidence when responsibility for a collision is considered.

For this exact question — “What is a yellow box junction and when can I enter it in Northern Ireland?” — the practical point is: Judge the available space before crossing the box line, not after you are already committed. The answer should be applied to the actual signs, conditions, licence wording or parking rules in force at the time, because temporary restrictions and individual DVA decisions can change the ordinary position.

This Northern Ireland-specific page on “What is a yellow box junction and when can I enter it in Northern Ireland?” was checked against the attached official sources before publication, with nidirect/DVA and the Northern Ireland Highway Code used ahead of generic UK motoring articles. If the rule, road layout or personal licence condition changes, those primary sources are the ones to re-check.