In which situation is it critical to let other drivers know you are slowing down?

It is crucial to let other drivers know you are slowing down, especially in the context of stopping suddenly or unexpectedly. When such situations arise, other drivers may not anticipate a sudden decrease in speed, which could lead to rear-end collisions or other types of accidents. Communication with other drivers, through brake lights or hand signals, provides them with a warning that you are about to stop. This is vital for maintaining safety on the road, as it allows adequate reaction time for following vehicles.

In the other scenarios, while signaling your intention to slow down is important, the critical nature is more pronounced during sudden stops. For instance, on a highway, other vehicles typically keep a greater distance, and a slower speed is somewhat expected when maneuvering around corners. Turning right at intersections often involves decelerating gradually, where signaling your intent is understood as part of normal driving practice. Exiting parking lots also usually indicates to others that you will be slowing down, but again, this is often a part of the expected behavior in that context.