An interesting article. I've come across these a couple of times while travelling about: http://www.rugbyadvertiser.co.uk/news/local-news/the-rise-and-rise-of-the-average-speed-camera-how-they-work-and-what-you-should-know-about-them-1-7411994

It's very easy to get caught by them. You tend to forget that you're being monitored.

I often forget about them, but haven't had any letters from the police yet, so my driving can't be that fast!

Over 40 years and still got a clean licence - Likely more by good luck than anything else, plus I rarely drive these days.