This can give you an indication, but it has flaws. For example I live in Utrecht and this map counts a lot of empty farmers land as parts of Utrecht. So in the overview it looks as if Utrecht has bad accessibility, but if you zoom in and take a look at the actual urban areas you'll see that they have very good access to services.
If you look at Paris for example, most regions they count as city are indeed urban areas.
Also it counts Ijsselstein en Nieuwegein as parts of Utrecht, even though they are separate cities. But I get why they did that.