Garbage Trucks and Couriers

Do garbage truck drivers have a secret alerting system that tells them when I'm approaching? Seems every time they have to reverse out onto a busy street, I'm alway the one driving straight for them. Then, I have to slow down, or hit them. And seeing as I'm not in an armored vehicle, hitting them aint an option.

And Couriers. In particular, Fed Ex today. Why do their turn signals never "work"?