For AI agents: use /llms.txt for the Nakafa content index.
Stopping distance is the total distance a moving object needs until it fully stops. For a vehicle, this distance does not only happen while the brakes are acting.
Before braking begins, the driver still needs reaction time. During that time, the vehicle keeps moving forward with its initial speed.
So stopping distance has two stages. The first stage happens when the driver notices danger but the vehicle has not started braking. The second stage happens after the brakes act and the vehicle slows to a stop.
| Part | What Happens | What Determines It |
|---|---|---|
| Reaction distance | The vehicle still moves with its initial speed | Speed and reaction time |
| Braking distance | The vehicle slows until it stops | Initial speed and deceleration magnitude |
While the brakes act, the vehicle slows down. If the deceleration is treated as constant and the final velocity is zero, a uniformly accelerated motion equation can be used to find the braking distance.
The quantity is the magnitude of the deceleration, so it is written as a positive value.
This formula uses a simple assumption: the path is straight, braking deceleration is treated as constant, and the vehicle does not skid. If the road condition changes, the value of can change too.
Reaction distance is directly proportional to speed. If the speed doubles, the reaction distance also doubles for the same reaction time.
Braking distance is more sensitive because it contains . As speed increases, the motion energy that must be removed by the brakes grows much more quickly.
Suppose the reaction time is and the braking deceleration magnitude is .
| Speed | Reaction Distance | Braking Distance | Stopping Distance |
|---|---|---|---|
When speed rises from to , stopping distance rises from to . It is not just doubled because the braking part follows the square of speed.
A vehicle moves at . The driver's reaction time is and the magnitude of the braking deceleration is .
So the vehicle needs to stop under those conditions.
That is not only the distance after the brakes are pressed. The first happens before braking starts, and the next happens while the vehicle is braking.
