The Prius actually has this same beeping while in reverse - but one can only hear it in the car. It's not piercing, but I'm not sure it serves any real point either.

I don't get the earlier comment: "You simply do not care about morals, children, and society in general." - why do disagreements suddenly become moral issues? please. Does this person actually think a child would think oh - a truck is backing up so I should feel that the driver is serving the morals of this country? If one is in an urban environment where this annoying sound is one of many sounds, does one actually believe that everyone is going to filter this sound and move out of the way of a truck going in reverse? Do pedestrians actually stop walking in the crosswalks when they're not supposed to? No. Perhaps a flashing bumper light might help, but not really if we overuse lights Vegas-style. It just gets filtered out. Too much is just too much.