If I'm going less than three miles, I'm fine with not having anything other than the bike. I might bring stuff, and I might not. That includes a helmet and a water bottle. If I'm going three miles or more, I want water and the ability to fix a flat and do other small repairs. I've been getting a bit lax about wearing a helmet, and I'm working on being more consistent, because I could get hurt even on a short ride, but I also don't think it's the most important safety item.

Don't forget trouser bands if I'm wearing long pants.

I really do like to use a rear-view mirror. I use the kind that attach to my glasses. It folds up and fits in my pocket or backpack.

All of my bikes -- and I have many -- have bells on them.

The bike I ride the most often has dynamo powered lights. They come on when the bike rolls. They turn off a few minutes after I stop riding, thanks to built-in capacitors. I supplement these lights with a battery-powered taillight and sometimes a battery powered spoke light.