Dear Mr. Driver of Large Trucks,
I fully appreciate that when informing clueless drivers that they have just made an illegal and dangerous lane change that the air horn is an extremely efficient tool. However if your ultimate goal is to improve the overall safety of the road, you might have a thought for the effect that air horn has on the bicyclist you are immediately behind.
No love,
HRJ
P.S., If overall road safety is your goal, try to avoid cutting the inside curve so close that the bicyclist has to go up on the sidewalk to avoid getting sideswiped when you're passing her.
(The freeway foo has ended up dumping a significant number of commuters onto my route home. They're all frustrated and cranky. My only satisfaction is zipping by them on the bike.)