I’ll add a note to the map to promote a re-survey and hopefully someone will go and take another closer at the surface soon.

Yes, there is a bit of a fundamental tension here. Data consumers want a restricted set of well-defined values for things, but unfortunately the real world has a long tail of odd ways of building things which won’t fit within that set. For an area like Lancaster which has had a reasonable amount of QA done on its map already, the rare surface values that remain are probably there for a good reason.

Personally I think that MapRoulette tasks like this one should only be used to fix obvious typos in surfaces. Anything more than that needs an in-person survey to check what the original mapper meant with their tagging. It can be quite hard to decide between “was the original mapper aware of this other, more standard, surface tag, and they deliberately didn’t choose it for some reason; or were they unaware of it and would have used it if they’d known about it?”.

There’s some discussion of this topic on the wiki: https://wiki.openstreetmap.org/wiki/Any_tags_you_like

Anyway, thanks again for your work on improving the map. I see a number of your MapRoulette edits in the area I’m interested in, and most of them have been obvious and welcome improvements. :D