I've never seen anyone do that in the UK. It would be illegal anyway but people don't even speed up and slow down. Which countries are you talking about?
Speed on a long stretch between boots, go to the gas station. Average speed is ok, still quicker at the destination.
Can't particularly recommend it, but it does happen.
Pro-tip: bring enough cash to pay the fine, because the police will drive you (slowly) to an ATM if you don't have enough to pay the fine.
Italy is one country they implemented it, I asked my friend in his BMW if this is the best this bad boy can do and he said with a sad Italian voice, "There's no point Tibor"
Not just motorways they are all over the place, I use Waze on my motorcycle with a blue tooth headset and it announces them as you enter leave and shows a moving average (which I'm always way under, I don't speed but I like to know where they are because they can make cars erratic, same with speed cameras, if I get the alert there is one ahead you can predict all the cars will start braking earlier).
Honestly I'm completely in favour of both speed cameras and moving average zones, the stuff I see on a week to week basis is shocking, same with red light cameras, I wish every major to minor junction had them.
Yes of course. I never said they don't - I was doubting that people pointlessly speed and then stop and wait for their average speed to drop. It sounds implausible.