Go on the highway, somewhere in the city, where it looks like you are in the desert and on the right side of the highway, there is a spot with a ledge.

Find the ramp onto the ledge and stay up there using your car as a shield so the police dont shoot you.

It will take a while for the police to get you... all the officers get out of their cars and walk towards the ramp.

Now jump off the ledge and drive away in a police car!