The change in regulations might make it cheaper to implement 20 mph limits but at the expense of drivers who do not notice. It is difficult enough in unfamiliar town centers when a driver is trying to follow signs to the town center, car parks, visitor attractions and making sure he is in the correct lane let alone noticing the reduced speed limit to a surprising 20 mph. I have on a few occasions only noticed the 20 mph limit on leaving a zone. I like to follow the rules but need to know what they are so I can follow them.