I would like to think that most people would like to be courteous when driving and that many people may not be aware of some of the unwritten rules on the highways that can make you an even more polite driver. When a large vehicle passes you and you would like to let them know they have safely cleared your vehicle you can turn your headlights on and off or off and on a couple of times. Unless it is full daylight out please do not flash your high beams (brights) as this can cause temporary blindness of the driver who just passed you. If you pass someone and they flash their lights to let you know it is safe to come back over into the main travel lane you can say thank you by flashing your 4 way flashers for a count of two. Semi trucks may also say thanks by turning off their trailer lights briefly. They have a switch in the truck that allows for this without turning off their headlights where cars don't, so flashing your hazard lights for a 2-3 count works just as well. If you are traveling in a group and pull into a rest area take up as few of the parking spaces as possible in the truck/trailer lot. The spaces in those lots are usually 80-100 feet long so often times 2 TV with small campers can fit into a single space. This leaves more parking for those vehicles who need a full space like large motor homes and trucks. If you see a vehicle stopped on the shoulder of the road, move over into the other lane if possible. If not possible slow down some. Pretty much all states have laws that say to do this for emergency vehicles (police, fire, etc) and some include road crew trucks and tow trucks in this as well. Regardless of what the law in any given state may say it is the polite thing to do not to mention it adds a huge degree of safety for both you and the vehicle and occupants of the vehicle on the side of the road. When it comes to sharing the road with large vehicles there is a simple rule to remember. If you can not see the driver in the mirror of the truck then the driver can not see you.