First, you'd want to convert the vehicle's velocity to meters per second.
Next, you want to see how far the car traveled before the driver hit the brakes. The equation for that is something like this:
[math]x = vt[/math]
The distance = velocity * time.
The distance traveled after the driver hits the brakes is weirder. The equation I've used is this:
[math]V^2 = V_0^2 - 2a(x - x_0)[/math]
Where V2 = the final velocity (squared) (which is 0, because the car is stopping), V0 = the initial velocity of the car, a = the acceleration of the car (the breaking rate), and x - x0 is the distance it travels.