First off, I don't know what the laws are were you are, or were you are.... but there is prob. a leagal distance that you need to be away from any people before baiting. the second thing is that if you are sure there will be rec. campers near by, is it worth it to draw bears to that location? They may already be there, but adding fuel to the fire may be dangerous for children camping near by, and may not be very responsible on your part.
However, if you are a leagal distance away, with your bait site properly marked, and feel you won't cause a threat to an inocent people. I figure that as long as when your in your bait site, you don't hear any voices(in your head or otherwise..lol), or people don't accidently hike by, you should have no problem with the distance from the major road.
the bears will be used to the car noises so that won't factor in.

Bears are generaly timid of people, and we want to keep it that way for all involved, so be very certain that before you draw more bears to the area, and posibly associate the bait site to the campsite, that you are certain that it is responsible hunting. I didn't mean to rain on your parade, but I know how dangerous these animals can be, and I'm sure that down the road a couple of miles there is prob another great spot.