There are so many factors which works to stop a car from sinking into road surface. One is reaction force other factors are density of material from which the car is made of, mass and shape of car.but the most important force is the reaction force. According to the Newton's 3rd law of motion:- every force have equal force acting in opposite direction.
I believe it's technically referred to as the Normal force. However I like to think of it as the reaction force, as it is the force that is a result of obeying Newton's 3rd law ("<span>For every action, there is an equal and opposite reaction"). The upward force from the ground is the reaction to the downward force of gravity.</span>
