Stopping sight distance, How do you calculate stopping sight distance ? , What is safe stopping sight distance ? , What are the factors affecting stopping sight distance ? , minimum stopping sight distance as per IRC

Stopping sight distance

Stopping sight distance (SSD) can be understand with the help of example so suppose that you are driving on any highway and suddenly you see an object ahead of you and to avoid collision to that object you applied brakes to stop the car. Hence the distance required for stopping the car to avoid the accident is called Stopping sight distance. 

Stopping sight distance is the minimum sight distance available on highway on any spot having sufficient length to enable the driver to stop the vehicle travelling at design speed , safely without collision with any other obstruction. 

Stopping Sight Distance = Lag Distance + Braking Distance

What Is Lag Distance ?

Basically when driver observe any obstruction then his or her mind takes some time to react to that situation that reaction time is in few seconds , so the distance traveled during reaction time is called lag distance. 

Lag Distance = v x t 

v - design speed (m/s)

t - reaction time

What Is Braking Distance ?

After processing the thought in mind now it's time to apply brakes hence distance traveled while application of brakes is called braking distance. 

Stopping Sight Distance

Suppose F is the frictional force and L is the braking distance then 

work done against friction is FL = fWl

                                  W- Total weight of the vehicle 

The kinetic Energy at design speed is
                   

Therefore the Stopping Sight Distance (SSD) = lag distance + braking distance 

v - design speed (m/s)

t - reaction time in sec.

g -  acceleration due to gravity 

f -  coefficient of friction 

                  

When there is an ascending gradient of say +n%, the component of gravity adds to braking action and hence braking distance is decreased. The component of gravity acting parallel to the surface which adds to the braking force is equal to Wsinθ ≈ tanθ ≈ Wn/100