Explain the Stopping Sight Distance

Stopping Sight Distance Is the Sum of Two Distances

(1) The distance traversed by the vehicle from the instant the driver sights an object necessitating a stop to the instant the brakes are applied; and

(2) The distance needed to stop the vehicle from the instant the brake application begins. 

These are referred to as brake reaction distance and braking distance, respectively.

SSD = 1.47V_mpht + V²_mph / 30 ((a/32.2) + G)

Where:

SSD = Stopping Sight Distance, ft;

V = design speed, mph;

t = breaking reaction time, 2.5 sec²

a = deceleration rate, 11.2 ft/sec

G = percent of grade divided by 100, it is in decimal

First part of the equation represents brake reaction distance and the second part represent braking distance.