The additional resistance for plastic roads, in contrast to the rolling resistance on a rigid road, increases with an increasing tyre pressure, since the tyre contact area is lowered by an increased inside pressure and the tyre sinks deeper into the ground.
In total, the wheel resistance results from the sum of the resistive force generated as a result of compacting together and displacing the road surface, by track rut friction, and by the rolling resistance occurring on a rigid road: