What does a yellow traffic light indicate?

A yellow traffic light indicates that the light is about to turn red, and drivers should prepare to stop. This signal serves as a warning to alert drivers that they need to make a decision about how to proceed safely. When encountering a yellow light, drivers are expected to slow down and stop if it is safe to do so, rather than trying to rush through the intersection. This action helps to prevent potential accidents and ensures that all drivers are aware of the upcoming change in traffic signals.

The other options suggest interpretations that do not align with standard traffic rules. Assuming the light is about to turn green could create confusion and lead to unsafe situations. Proceeding with caution is appropriate advice, but it does not encompass the need to stop, which is the primary intent of a yellow light. Finally, suggesting that drivers should speed up contradicts the safety measures intended by traffic signals and could result in dangerous outcomes.