Sorry to say after my naughtycourse earlier in the year (34mph in a 30, a few yards from a 40 zone, the child-killer that I am) that I spend much more time watching me speed, and less time watching the road. I have no desire to speed, no desire to cause hurt, however, have I even drifted over the sped limit by 1mph or two? Yes, of course!!! Every has, and will continue to do. But I spend lots of time glancing down at my speedo, literally paranoid that just over my shoulder there's a copper watching me. That's great until you miss things in front of you.
I was taught in my driving lessons to check my rear view mirror once every ten seconds. I remember one incident when a car pulled out from a side turning in front of me, and though not quite accident-causing, the instructor did have to knock 10mph off our speed with the dual controls to avoid a bump. When he said 'don't worry, just eyes on the road' I pointed out 'I was checking my rear view mirror' he didn't have an answer. Sorry, but a moment's distraction, be it checking your stereo, turning to your passenger, checking your change, whatever can be the difference betwen a collision and a near-miss.
All the speed-watching in the world won't alter the reaction times of someone whose attention is elsewhere in the first place. Offer me the driver who is doing 33mph and watching the kid darting out into the road, and applying the brakes sharply, or the 29.9mph driver who idly noticed the kid standing on the pavement, then looks down for half a second, maybe a second, only to look up, to see the kid in front of him, and I'll take the first guy anytime.
You travel 13.5metres/45ft in a single second at 30mph. One second looking down at your speedo, to check you're doing bang on 30, and not drifted over by a fraction. Compared with someone doing 33mph, they've done only 4 1/2 feet more. But Mr 33mph's eyes are on the road... on the road for all those 45feet that your eyes and attention are elsewhere... Just food for thought.
I'm not advocating speeding as a right, just the reasonable, practical and fair method of its determining what is 'unsafe'. Doing someone for doing 71mph in the name of safety is the same as a Hollywood celeb buying a new Prius every year in the name of being 'green'.