Average speed cameras are common in the UK. The flow of traffic adjusts so that the body of traffic is at the limit - we don't keep our eyes on the speedo, as e

Average speed cameras are common in the UK. The flow of traffic adjusts so that the body of traffic is at the limit - we don't keep our eyes on the speedo, as enforcement only kicks in at limit+x mph, and a short duration deviation from speed isn't a problem. Most people have cruise control, and they won't need to check the speedo once set. I've no empirical evidence, but driving on main roads with average speed cameras feels safer.