To unlock the Dozing trophy in RAGE 2, you will first need to find the Dumper Truck, which is a front end loader vehicle. You can find the Dumper Truck at a roadblock to the left of Gunbarrel.
You can raise and lower the Dumper Truck's bucket by pressing
. Lower the bucket, drive around until you find an enemy, drive into them and then hold
to raise the bucket with the enemy inside.
You might have to practice a couple of times with the speed that you approach for it to work.
You can find a video below showing the location and method (credit to Apache on YouTube):