The trophy for running over dismounted drivers is a hard on for me to get. Is there any way to do this easy? The only time I hit someone is by chance! And after I lost my data i have to restart the number of hits! I had 6 out of 10, now 0 out of 10! What to do?

Pick a race with a lot of bikers and ATV riders, and then stay near the back of the pack. Some get inevitably knocked off at the very start, so run over them.

You can use either a buggy (great because it is maneuverable) or an ATV to do the challenge. ATV works because you can punch them off, and then run over them. Buggy works if you use nitro to knock them off sideways and then run them down.