50% of the deer killed at my camp are killed on roads, either in a chair or vehicle as described above. The problem is judging the distance quickly because you only get a few seconds. After Halloween a few years ago we bought plastic pumpkin baskets for trick-or-treating for 50 cents at Wal Mart. Drill a few holes in the bottom and put a scoop of dirt in them. Put them out every 200 yards on the side of road where you can see them from your set up. It is the quickest way to determine if they are in range. If you see them crossing near the third pumpkin you know they are out of range but you also know where to move your stand next time.