What indicates a driver must stop before entering an intersection?

A red traffic light indicates that a driver must stop before entering an intersection because it signals that traffic must halt in order to allow for the safe passing of vehicles and pedestrians in other directions. Traffic lights are designed to control the flow of vehicles and optimize safety on the road. When the light is red, it is a clear instruction that stopping is mandatory, preventing potential collisions and ensuring that all road users are considered.

While a yield sign suggests that a driver should slow down and prepare to stop if necessary, it does not enforce a full stop like a red light does. A speed limit sign, on the other hand, merely advises on the maximum speed at which a driver should travel, and a green traffic light indicates it is safe to proceed. Therefore, the presence of a red traffic light is the definitive signal that stopping is required.