This is only difficult if you don't know what you're doing.
You must run into things. Don't wait for cars to hit you.
Hop into a car and go to the blue bonus areas and ragdoll fall into cars (LT or RT). You want to be like a pinball and hit as many cars as you can in each fall. When adrenaline mode activates, the yellow bar will slowly deplete. Look for lines of parked cars or cars waiting in a line and jump headfirst into the first one, then use the moon physics to hit all the cars over and over. Eventually the blue zones will deplete, and you should move on to another zone. It isn't worth looking for police cars or hitting things head first to eject from the windshield. Find an intersection and run at the cars.