A good rule of thumb is to pretend you are invisible to motorists, because effectively, you often are. When motorists feel threatened by other motorists or trucks, their mind will prune details from the field of vision so as to reduce the load on the brain and ease the decision-making process. Typically, this means eliminating everything except the other cars/trucks and the outlines of the road. Bicyclists, motorcycles, pedestrians, potholes in the road, street lights, stop signs--all that gets filtered out, regardless of what color your panniers or vest is.

This is why I prefer traveling mostly on dirt roads with very few motor vehicles. Not an option for everyone, I know. But definitely possible here in the Great Basin area. Very few people biking in this area, probably because they're afraid to carry massive amounts of water.

Sometimes I am forced to travel on highways and these have narrow or non-existant shoulders. I always prepare to either stop or to ride the bike off the road into the dirt when things get tricky, such as two 18 wheelers passing in opposite directions with no room left for me. Doesn't matter if they see me or if I have the right of way. 18 wheelers can't stop quickly even if they try.