Drivers. Uggh. It's not the four wheels that cause trouble - it's the fifth one in the hands of someone just itching to slip past you, eager to make that right turn.

So a bit of advance warning is useful, and that's why bicycle mirrors are genuinely useful. Few cyclists have them, perhaps grouping them with bells and baseball cards as kid-bike add-ons. But mirrors will keep you out of trouble, and give you a more relaxed journey in the process.

This bicycle mirror from Mirrycle doesn't look very high-tech, but it's top-rated on Amazon right now: 4.5 stars from 30+ reviewers. The assembly process is a little tedious, but results in a mirror that will hang tight to any bar design, and won't vibrate as you ride, buzzing your image.

Mirrycle MTB Bicycle Mirror, about $13 at Amazon.