Good spot – I’ll take a look. cycle.travel is fairly selective about using non-NCN route numbers in the UK because historically OSM mappers have been eager to make up names/abbreviations that aren’t signposted at all on the ground, or are only signposted intermittently. But it’s probably something that needs looking at again.

Currently cycle.travel only shows route refs in the instructions, not names. I’d like to give it the ability to show names, but that’ll require reengineering OSRM’s street name storage and I always need to pluck up the courage before diving into nested C++ data structures…!

I think intermittent signposting is a worldwide problem and in the UK, I suspect NCN routes suffer more from it than council LCN routes - but I think there is no easy way in the OSM data to distinguish council routes like Norwich's from charity ones.

Displaying ref should be OK but I guess another problem in Norwich is that they do not currently have ref set. I am unsure why that is and will dig a little deeper. It looks like it was removed in https://www.openstreetmap.org/changeset/33398857 - any suggestions why?

And just elaborating on "no easy way" - it is possible sometimes to detect a council-run LCN by the website tag including ".gov.uk" - but I do not think that is easy.

What I’m most wary of is where enthusiastic, well-meaning campaign groups (or individuals) have mapped their ideal local cycle network… but it’s not supported by any signs on the ground. So, for example, in Oxford you can see these lovely numbered routes: https://cycle.travel/map?lat=51.7421&lon=-1.2321&zoom=17 . That’s great… but they’re not signposted on the ground, at all. I don’t want to give people directions saying “turn left along route 5” when there’s no possibility of any route 5 signage! It probably needs a serious OSM gardening project.

If there are no signs on the ground at all, the network should be tagged proposed or similar and I think that's a bug on OSM. Yes, that's unhelpful behaviour by the mappers, but I think it's throwing the baby out with the bathwater to refuse to show a whole class of real routes as a consequence of some local errors.

Locally, we do have a problem where the outlying parts of the network have been signed with route numbers but the urban parts use destinations and only show national route numbers, not local or even regional, with government not planning to amend signs unless damaged, but that's an error by our government which is much more difficult to handle. As noted, if you refuse to show all local routes, some of the turn-by-turn directions become useless.

And now I notice that where we've also put the cycleway names and numbers into OSM mainly to ease reporting of problems, cycle.travel shows those numbers and names, which appear on signs even less often than the local route numbers!

Yes – really OSM should only contain those routes that are signposted on the ground. A signposted route with unsignposted numbers should have them tagged with something like ‘admin_ref’ rather than ‘ref’, and so on. Otherwise it’s pretty much impossible to work out how to give the right directions.

Do you mean "official_ref" where you wrote "admin_ref"? I will update the Norfolk Y-road numbers to use that and probably "official_name" with the locally-known name as "name" rather than "alt_name" where they differ.

I am less sure how much of a route should be signposted with numbers to before we use ref instead of official_ref (or lcn_ref?). For the few which are signed throughout or do not appear at all yet (as far as I know), it is an easy decision for now. For those which appear on part of a route (5 and 9), splitting the relation would be easy although it might need changing later, but those that appear intermittently (including national 11, regional 30 and local 6) will be a nuisance.

official_ref works, yes – historically there’s not been much of a consensus which one to use but official_ref seems to be winning out. If they’re intermittent then I’d suggest tagging them anyway – might be a bit of a prompt to the relevant authorities/volunteers to fix up the missing sections!

Thoughts about "unsigned=yes" on route relations? I noticed it being used for Cycling UK's Great North Trail MTB superroute.

It’s a good idea! That’d definitely help in identifying which routes are worth including in turn-by-turn directions and which aren’t.