[h=2]Common issues when cycling[/h]
There's one issue which everyone deals with but hasn't been fully solved: knowing what's behind you. Sure, people swear by their helmet mirrors or bar mounted mirrors, and some just listen and turn their heads but realistically all of the solutions are half measures.

You didn't ask for solutions, but take a good look at a rear facing wide angle camera and google glasses or something similar for a heads-up display.