Does a green traffic light mean you can enter a blocked junction in Northern Ireland?

No. A green signal does not permit you to enter if you cannot clear the junction safely.

Highway Code rules on junctions require drivers to avoid blocking roads and crossing movements. The colour of the light tells you the signal permits movement; it does not guarantee the exit is free. If traffic is backed up beyond the junction, wait behind the stop line until enough space appears on the other side. Do not stop across a pedestrian crossing or obstruct turning traffic simply because the light was green.