That’s why there are 3 mirrors so that you can see what is coming up behind you. Remember – mirror, signal and if clear execute.I gave up driving when I developed vision problems. Technically and legally I can still drive but I know I'm not safe as I can't always see things approaching from the side so I could be unaware for example that something was overtaking me and I could pull out into its path.
A competent driver should not only know what is ahead but also know what is coming up behind.

