In the above diagram, all vehicles stop mainly because of?

The above diagram shows a zebra crossing, which is a designated area on the road where pedestrians can cross safely. All the vehicles in the diagram have stopped mainly because the pedestrians have already stepped on the zebra crossing. This is because the zebra crossing is specifically meant for pedestrians to use, and it is illegal for vehicles to drive through when pedestrians are using it. Therefore, drivers are obligated to stop their vehicles and give way to pedestrians using the zebra crossing. This is a safety measure to prevent accidents and promote the safety of pedestrians.