The govt should have their cars impounded for letting lawyers interfere in science and engineering problems, they're so afraid of the fact these systems aren't perfect (nothing ever is but nor does it need to be) they try to hide the mechanics of this shit behind layers of bureaucracy, instead of clearly explaining how this all works, where it can fall down, but also the checks and balances in place to pick up when and where it does... but most importantly doing it in plain english.
Kalel's given you all lesson on the science, and I've worked closer to all this than I care to admit on a motoring forum, the above is tied up in politics and a general disrespect for intelligence of their voters.
But at the end of the day you all know when you've been speeding, personally I've been done three times, and I was in the wrong each time. If you have a GENUINE doubt then pursue it like anything else, but if you KNOW you were speeding take your lumps and stop whining (this isn't directed at any one in particular I must stress), don't fight it coz it makes ratings for Today Tonight.