On a solo ride this weekend, I was noticing how I use my mirror. It only takes me about 1/2 second to slightly turn my head to aim the mirror straight back and glance back to see that the road is clear. It's more like 1 to 1 1/2 seconds to sweep from side to side, a field of view at least 90 degrees wide to the rear.

So a quick glance is fast and easy, and I don't lose track of what's going on ahead of me. I can do this way more often than I would turn my head far enough to clearly see the lane behind me. It's just about the same amount of time as using a car's side mirror.

But I still get surprised by cars passing sometimes. I don't always look back when the road isn't busy. And wind noise usually covers the sound of car tires when I'm faster than 15 mph.

If a car has slowed to wait behind me, I'll usually turn my head and fake a look back, so the driver knows that I'm aware of them.