I stopped at a roundabout today because the driver in front of me decided to let the two loaded tractor trailers at the next road enter first. I don't usually use my horn, but today let him know that he needed to get moving before the second truck entered. We then proceeded to follow the first truck for 10 miles at 5-10 mph under the speed limit. Nothing was accomplished by his pseudo courtesy. In the time it took him to let the truck know to proceed we both would have been through the intersection.