not this time ... heavy rocks are being thrown at high velocity from a passing pickup truck ... if both vehicles are traveling 60 mph, the striking rock has a 120 mph relative velocity ... the five recent instances in the denver area have happened several miles a part ...
Your math skills suck. If both car are traveling 60 mph in the same direction and you throw a rock 5 mph faster relative to the earth your rick is traveling 65 mph, relative to the other car it is traveling 5 mph.