As a South African, I find the UK's insistence on making speed traps visible completely bizarre. The whole point is to stop people speeding. Defeats the point entirely if you speed along until you get to the conveniently highlighted camera, at which point you slow down.
You do need eyes in the back of your head to spot police with a radar gun. We saw one lying in a storm drain, virtually invisible. OR, just a thought... you could.... wait for it this is a big one.... NOT SPEED?! Then the police could hide wherever they want and you would not get any fines.
On that note, speeding in most places in SA is stupid. This is a developing country. Roads are generally surprisingly good, but there are people and animals on the weirdest roads at the weirdest times. There's also a lot of traffic and a lot of vehicles that are barely road worthy. Plus, let's be honest, there are a lot of people who probably shouldn't be driving in the first place. Keeping to the speed limits will keep you, and others, safe.