Make Car Respond to Different "Terrains"

Hey Everyone,

I’ve been working since August on my Senior Design project for graduating in May with a Bachelors in CS. I am stuck on one of our last issues for this semester; cause the car to actually interact with the terrain below it. For example, if we paint the terrain to look like ice or dirt or grass, we want the car to be able to slip when it reaches the ice, or drive slower depending on whether its on grass or dirt.

Does this make sense? I am using the example as the outline for our vehicle.

Thanks! I have really enjoyed looking through the forum here for help with previous issues.