I have a nice mirror on my bicycle, and I use it just like you said.
If I see anything back there, I know about what and where etc.
But if I see nothing, I still have to take that quick rubber-neck to make sure.
It's real nice for riding on narrow bike paths. It's a good heads-up when those dang
racing bikes come shooting up behind us going about 25!
Many of the speed-boys yell, "On your left".. But some don't..
100 MPG sounds pretty dang good! I saw a 2-stroke 50cc Zuma in town today.
The owner says it's pretty fast and does very well on the hills.
He was a big guy and he was zipping right along, the last time I saw him..