What does a red traffic light signal?

A red traffic light signal indicates that drivers must come to a complete stop at the intersection before the stop line or crosswalk. This signal is crucial in managing traffic flow and ensuring safety by preventing vehicles from entering intersections when it's not safe to do so. When the light is red, it means that vehicles coming from the opposite direction may have the right of way. The requirement to stop helps reduce the risk of collisions and gives time for pedestrians to cross safely when applicable.

The other options suggest actions that do not align with the rules associated with a red traffic signal. For instance, proceeding with caution would imply that it is safe to move, which conflicts with the fundamental purpose of a red light. Yielding is about giving way to other road users, which doesn't apply when a red light is present, as it demands a complete stop. Turning left only could be a specific traffic regulation but is not the general rule associated with a red light, which prohibits all movement forward.