he has applied common sense.
You may be right, he has applied common sense, unfortunately connecting common sense and good sense in this context and many others is flawed.
but forcing a driver to spend more time watching the speedo than the road will cost lives.
What evidence do you have that people who are trying to keep within a 1km/h tolerance of the speed limit are driving blind and just watching their speedo?, their are plenty out there now doing exactly that.
Really, dont we all drive by observing what is around us, a glance in the rear view every 15 secs or more, the speedo in most cars is right under driver's nose within peripheral vision anyway, its not like you have to turn around to look a the frigging thing. perhaps we should stop mirror checks too?
Its pretty easy to keep your speed within 5 ks of the limit though, still checking the speedo regularly of course but not having to stare constantly at it.
So what's the problem with doing that then?
You still need to have a margin for error built in, to allow for tyre wear, instrument inaccuracies, and the force of gravity slowly speeding you up down a hill...
People know that if they have an old car that their instruments could be out, either do 10% less than the limit because you dont know, or get your instruments checked out so you do know, ignorance shouldnt be an excuse. Do people think all the instruments on their car are 100% accurate? how many cars run out of petrol as soon the instant the needle hits empty? ffs.
Those whose instruments prove to be more than 10% undereading by no fault of their own perhaps have a case, but really, that would be pushing reality to find even a few of these people. Basically if your car is undereading by 10% or more and you havent figured it out for yourself then maybe driving is too complex a task for them.
Tyre wear, not an issue, the speedos are designed to not underead with new tyres on them, as the tyre wears all that can happen is that the speedo will overead.
Speeding up down a hill? ffs, for those that are driving and become so detached from the surroundings that they dont notice a hill? best we get these people off the road, a few speeding fines would speed up the process. (perhaps they'd be more observant of hills when they are on a pushbike!)