Continually turning round to check on following or overtaking vehicles would take your eyes off the road ahead and be distracting. That’s what your mirrors are there for, to be aware of what’s behind. Use your mirrors before any manoeuvre.
Knowing what’s going on behind you can be just as crucial to your safety (and enjoyable riding) as observing what’s ahead. So, as well as checking your mirrors before any manoeuvre, you should regularly check your mirrors as you ride.
You should have a thorough awareness of the traffic situation behind you and how it’s developing. Are you being caught by other vehicles? Is someone overtaking behind you and liable to catch up? Does the vehicle behind have enough distance to stop before hitting you?
Use regular mirror checks to understand the picture behind you. Once you develop your vision skills, your peripheral vision can add to the mirror checks and stay even more on top of developing situations behind you.
Knowing the situation and how it is developing behind you can let you plan ahead. For example, you might be thinking about an overtake but you can see another vehicle overtaking cars behind you. Will it catch you around the time you anticipate being in an overtaking position? If so, a risky situation could develop. If you know where that other vehicle is, you can better plan your own riding.
Know your blind spots and stay alive. These are:
Even when you’ve checked everything is clear in your mirrors, just before you turn left, turn right or move into another lane, you should do a ‘Lifesaver’. It’s a quick glance (no more) to the appropriate three-quarters to ensure you haven’t missed something coming out of your blind spot and trying to pass you. Its name says it all.