I'll agree with one of swingset's points there. It really sucks when bicyclists (usually the ones in the flaming jerseys) ride two abreast knowing full well that a vehicle is approaching from the rear and don't go single file to let the said vehicle pass. I ride bicycle a lot & always ride in a lane position that will let car drivers pass without crossing the centerline. It's the courteous thing to do. I love it when I'm on my motorcycle when passing the arrogant "two abreast" guys. I just maintain speed, keep about 1 1/2 feet left of centerline & hold the horn button in from the time I'm about 10 feet away until I'm about 10 feet past for a nice dopler effect.