How to create varying areas of tracion for a racing game

Our small group is creating a racing game for a university project and we would like to create areas of different traction to create traps for the player. For example we have a puddle of wine that we would like to be slippy and cause the car to loose some traction and become harder to control.
We would also like to have an area where the car will become slower like a sand trap on real race tracks.

Many thanks
Alex