When is a driver forbidden to enter a pedestrian crossing?
Explanation
To protect pedestrians, the rules forbid the driver from entering the crossing until pedestrians have safely cleared their lane. Entering is also forbidden if it would force you to stop on the crossing, as that would block pedestrians from moving.
KET reference: KET 32: The driver is forbidden to enter a pedestrian crossing until the pedestrians who must be given way have left the lane it occupies, and also if there is an obstacle beyond it that would require stopping the vehicle.