Unless you are listening to headphones when you cycle, you should really be able to hear almost anything, except perhaps a slow moving prius, and even then you can hear the tires.

Anybody who wears headphones while riding is at a disadvantage IMO, because you can't hear anyone coming. No one can control what the car behind you is going to do except the driver, but when a car is approaching I do a quick check to make sure I'm as reasonably far right as I can be .