Commercial Driver’s License (CDL) Practice Exam

When traveling at 55 MPH, the time it takes to stop a vehicle depends on a variety of factors such as reaction time, braking distance, and road conditions. Under good conditions, the average reaction time for a driver is about 1.5 seconds. During this reaction time, the vehicle continues to move forward, covering a distance based on its speed. After the reaction time, the actual braking distance must be calculated, which varies with speed and braking efficiency. For a vehicle traveling at 55 MPH, the stopping distance typically includes both the distance covered during the driver's reaction time and the distance taken to come to a complete stop. When both components are considered, the overall stopping distance translates into a stopping time of approximately 6 seconds in total. This time frame can reflect the average and expected scenario for a driver traveling under safe conditions. Choosing the duration of about 6 seconds effectively considers both the initial reaction time and the necessary braking, making it the most accurate option for this scenario.