Question 1

What is average reaction time?

Accepted Answer

Average reaction time is 1.5 seconds for alert drivers. However, it can increase to 2-3 seconds or more if tired, distracted, or impaired. At 60 mph, each second of reaction time adds 88 feet to stopping distance.

Question 2

How much of stopping distance is reaction distance?

Accepted Answer

At highway speeds, reaction distance is often more than half of total stopping distance. At 60 mph with 1.5-second reaction, you travel 132 feet before even touching the brakes.

Question 3

How do grades affect stopping distance?

Accepted Answer

Downhill grades significantly increase stopping distance as gravity works against brakes. A 10% downhill grade can increase stopping distance by 20-30% or more.

Question 4

Why do trucks need more stopping distance?

Accepted Answer

Heavy vehicles have much more momentum to dissipate. A loaded semi-truck at 65 mph needs about 525 feet to stop - nearly twice the distance of a car. This is why trucks maintain longer following distances.

Stopping Distance Calculator - Reaction Time Tool