Just like how steel is tougher and needs guns or explosives to break, there should also be much weaker materials, this should be for grass and foliage, letting cars run through them without much hassle, so they don't get stuck on an extra centimeter of grass or some flower.
And it's not even just about weakness, grass and small foliage should straight up not collide with physics objects, period.

i'm like 99% sure the jeep/construction vehicles can drive through grass more easily than the normal small cars.
couldn't beat a mission on time cause the small cars kept struggling through grass but i switched to the jeep and it sped through.