I always ride solo, and am mostly on country roads or at least highways with four lanes so that I can take a lane. My usual training rides are a combination of both as I have to take the big roads to get out of the burbs to the country roads.
+1 to wearing a mirror. I need to know what is coming up behind me, but I also look back over my shoulder frequently , always if I am going to turn, or change into a turn lane, or am coming out of a side road onto a main road, I follow the driving rule of always look back over your shoulder in addition to checking in your rear view mirror. The trick is to train yourself to look back without swerving into the lane- it takes practice, but it can be done.
I also have a strong irregularly flashing red light on the left rear fork in addition to the one mounted on my underseat bag, along with helmet lights(all steady red) on the front and back of my helmet. That plus scads of bright, light, clothing. I would rather look like a dork than be injured. Of course that can't prevent the random accident but at least I am doing as much as I can to be visible.
marni
Katy, Texas
Trek Madone 6.5- "Red"
Trek Pilot 5.2- " Bebe"
"easily outrun by a chihuahua."