Washington State Department of Licensing Knowledge Test

When merging or changing lanes, maintaining a gap of at least four seconds between your vehicle and the one in front of you is recommended. This four-second gap gives you ample time to assess the space you need for a safe maneuver, react to any sudden changes in traffic conditions, and ensure that you can merge or change lanes without cutting off another driver.

The four-second rule allows for adequate stopping distance, especially in varying weather conditions or during unforeseen circumstances. It provides a buffer that accounts for the size and speed of both vehicles, enhancing overall road safety. A gap shorter than this may not provide enough time to react, increasing the risk of collisions.