This achievement isn't too difficult but it can be a pain. In Chapter 12 when you take control of the bus at the end, you have to avoid hitting the haunted on the road. Strangely hitting Cars does not negate this achievement. The part that makes it a pain in the butt is that there is no checkpoint before this. If you reload, you start after you grabbed the blood pack for Joseph. The other thing is, it is easy to miss the fact that you hit a haunted if you manage to get it with the side of the bus. This happened on my first attempt and I finished the level to realize that I didn't get the achievement. At that point I had to replay the entire level later.
The spawns are random though when I got the achievement, I found the sides were pretty good spots to be before spawning. It They do not tend to spawn there in groups and it usually gives you enough time to figure out what route to take before your next group spawns.