Sight Distance and Reaction Time
Sight distance is the distance from which you can see and identify a hazard, not necessarily the total distance you can see. You often see an object before you’re able to identify it as a hazard.
If the stopping distance to an object is greater than the sight distance, you’re in danger of hitting the object.
Reaction time is the time it takes you to react to a hazard. It involves these steps:
- Seeing something
- Recognizing it's a hazard
- Deciding whether to brake or steer around the object
Reaction distance is the distance the vehicle travels during your reaction time.
- The distance depends on the reaction time (in seconds) and speed (in feet per second).
- It is calculated as: Reaction Distance = Reaction Time x Speed
Accidents occur in just a few seconds, so think of your speed in feet per second (multiply mph by 1.46667).
- 15 mph = 22 ft. per second
- 30 mph = 44 ft. per second
- 45 mph = 66 ft. per second
- 60 mph = 88 ft. per second
At 30 mph with a reaction time of three seconds, the reaction distance is 132 feet (3 sec. x 44 ft./sec.).