As silly as this is, the expressions or the way people flinch/jump/startle when they hear a loud sound is kind of funny.
Just think how much bigger a set of horns you could put on a class 8 truck.
Here are two videos to watch people jump.
and these folks sell the horn kit and have a similar video
"I have marveled often at the thin line that divides success from failure and the sudden turn that leads from apparently certain disaster to comparative safety." Ernest Shackleton, Antarctic Explorer, Sea and Land, 1874-1922.