I used to work as a postman with a route that had a lot of driveways masked by trees or coming out at strange angles. For some reason whoever designed the postman motorbikes we used decided to make their indicators do the truck reversing beep when you used them. I lost track of the number of times I freaked out trying to work out where this reversing truck was coming from, especially since, judging from the sound, it was practically on top of me.