Wales (UK) did this about a week ago. Setting 20mph as a limit in urban areas. I was there yesterday and now the problem is that it's very unclear where exactly it applies and if it will be enforced. Also satnavs such as Apple and Google maps have not been updated for the new speeds leading to further confusion. There are some areas where this makes sense, but a blanket change seems political. Hopefully it will cause less pollution and accidents in the future and not just be used as a money making scheme for fining people.