Factors affecting stopping sight distance

The factors affecting stopping sight distance are:

1. Speed of the vehicle: the lag distance increases in proportion to speed and the braking distance with the square of speed.
2. Total reaction time of the driver (PIEV time): a longer time increases the lag distance; 2.5 s is adopted in design.
3. Coefficient of longitudinal friction $f$ between tyre and road, which depends on the road surface (smooth, wet, rough) and tyre condition.
4. Gradient of the road: a descending grade increases the braking distance, and an ascending grade decreases it.
5. Efficiency of brakes and the loading of the vehicle.
6. Weather and visibility: rain, fog, night; height of the driver's eye and of the object.
7. Driver characteristics: age, fatigue, alertness, alcohol.
8. Tyre type and condition.