Washington State Department of Licensing Knowledge Test

When driving at 55 mph, how long will it take you to pass another vehicle?

1. Five seconds

2. Ten seconds

3. Fifteen seconds

4. Twenty seconds

The correct answer is: Ten seconds

To determine how long it will take to pass another vehicle while driving at 55 mph, you first need to consider the lengths of the vehicles involved and the necessary distance for safe passing. A common guideline is that a vehicle needs to clear about one vehicle length ahead to safely pass. At 55 mph, the speed translates to approximately 80.67 feet per second (since 1 mile = 5280 feet and 1 hour = 3600 seconds). To pass another vehicle comfortably and safely, you typically require a distance equivalent to about two vehicle lengths (which can average around 40 to 50 feet for most vehicles). Using a rough estimate, to pass another vehicle you might need to cover a distance of 150 to 200 feet. If you take the average of 175 feet to compute the time taken: - Time = Distance / Speed - Time = 175 feet / 80.67 feet per second Calculating this gives roughly 2.17 seconds, which is clearly much less than ten seconds. However, if you consider that the entire process of approaching, passing, and returning to your lane can take longer—due to reaction time and safe clearance—the estimate aligns better with ten seconds for the whole maneuver.