Not 1950s, but 1970s; Lelystad. They did not mention this at all in the article, which is quite a miss. Lelystad was the earlier experiment, a bit more up north in Flevoland. It is not growing anymore because some parts have failed and not many people move there anymore. Housing is still quite cheap, even now. Some neighbourhoods are quite good neighbourhoods, some are just awful with many residents living on wellfare, many people into drugs, etcetera. They didn't plan for mixing different cultures and classes in society, they planned for somewhat segregated neighbourhoods, which was a wrong choice. If there is a city in the Netherlands where you can guess income and status from the postal code, Lelystad is the place.
We still have to see what will happen to Almere, Almere Haven is just 30 years old. Not all parts there are good :) It is often 30 or 40 years, that a neighbourhood can go from good to bad, at least that is usual in the Netherlands.
No love for the roads, but many of those brutalist buildings in Birmingham are considered masterpieces of architecture. That's why they are listed. And I can't think of one from before 1960, either.
