SSD = lag distance + braking distance\(SSD = vt + \frac{{{V^2}}}{{2gf}}\) ---(i)\(SSD = 0.278\;vt + \frac{{{v^2}}}{{254\;F}}\) ---(ii)When V is in KMPH eq (ii) can be used.v = design speed (m/s)t = decision time (generally 2.5 sec)g = acc. Due to gravityf = co-efficient of frictionCalculation:v = 80 kmphf = 0.36t = 2.5 sec\(SSD = 0.278 \times 80 \times 2.5 + \frac{{{{\left( {80} \right)}^2}}}{{254 \times 0.36}}\)= 125.59 m ~125 m.Other Important Points:Stopping sight distance (SSD) is also KNOWN as the ABSOLUTE minimum sight distance.Stopping sight distance (SSD) is also equal to headlight sight distance.Intermediate sight distance (ISD) = 2 × Stopping sight distance (SSD)