What is the average driver’s reaction time in seconds, leading to additional stopping distance at 55 mph?

The average driver's reaction time is generally recognized as approximately three-quarters of a second when traveling at a speed of 55 mph. This reaction time is crucial because it directly contributes to the overall stopping distance of a vehicle.

At 55 mph, a vehicle travels roughly 80 feet per second, meaning during a driver's reaction time of about three-quarters of a second, the vehicle will cover a significant distance of around 60 feet before the driver even begins to apply the brakes. This distance must be added to the braking distance to calculate the total stopping distance. Therefore, using three-quarters of a second accurately reflects the average human capability in a driving context, allowing for better planning and safety consideration on the road.