Let us say at the braking the vehicle speed was V.

At the moment that brake is applied the vehicle has a kinetic energy.This energy will be used for friction when it brakes and due to friction the vehicle stops.The braking distance is given by the skid length.

By law of conservation of energy we can say;

kinetic energy = work done against friction

`1/2*m*v^2 = mu*R*d`

`1/2*m*v^2 = mu*mg*d`

`1/2*v^2 = mu*g*d`

`v^2 = 2mugd`

`v = sqrt(2mugd)`

`v = sqrt(2*0.607*9.81*135.1)`

`v = 40.11m/s`

*So the speed of the vehicle had been 40.11m/s.*

** In terms of km/h the speed is 144.4 km/h**.

*Assumption:*

*All the kinetic energy had been used against the friction at the braking*