The total stopping distance of a truck or bus includes perception distance, reaction distance, and braking distance. These distances are critical in ensuring safe stopping under various road conditions and driver reaction times.
The three distances that make up the total stopping distance of your truck or bus are: 1) Perception distance, the distance your vehicle travels during your perception time, which is the time it takes for you to recognize a hazard; 2) Reaction distance, the distance your vehicle travels while you move your foot from the accelerator to the brake pedal; and 3) Braking distance, the distance your vehicle travels after you apply the brakes and before it comes to a stop.
An example to illustrate these concepts is as follows: if a truck is initially traveling at 30.0 m/s and the driver has a reaction time of 0.500 s, during this reaction time the truck continues at a constant velocity since there is no acceleration (areaction = 0). Once the driver hits the brakes, we calculate the distance AB (acceleration or deceleration path) without using the equations of motion because there's no acceleration before the brakes are hit. Then, we add the braking distance for either dry or wet concrete to obtain the final stopping distance.