I enjoyed posts of reaction time calculations & simulations of stopping distance. My question is: Two cars drive along. The front one at 100km/h. He gets hit from behind by a car with speed far exceeding that of the front car. The brake marks of the car behind measure 65m. Can we somehow calculate/estimate the speed of the rear car at the point of of impact and at point where he started braking? Both cars where average size family cars (max 5 persons) only 1 person in rear car. Had ABS brakes. Tyres in very good condition. How much impact would road & air temperature as well as tyre temperature have on the result?