When should drivers begin to slow down to the posted speed limit according to the signs?

The correct answer highlights that drivers should begin to slow down when they see the exit speed limit sign. This indicates the appropriate speed at which drivers should navigate the exit ramp. Typically, speed limits in these areas are lower than those on freeways to ensure a safe and smooth transition from the faster-moving traffic to a slower-moving area.

Recognizing the exit speed limit sign is crucial for maintaining safety, as it prepares the driver for the reduced speed necessary to navigate the turn or curve safely. Slowing down at this point prevents abrupt changes in speed that could lead to loss of control or accidents as the driver approaches the exit.

Other choices emphasize moments in the driving process where reducing speed is not immediately tied to specific signage indicating speed limits for the exit or transition to a different roadway, which might not allow for the gradual deceleration needed for safe navigation.