the DfT have sent me a spreadsheet containing detailed data about the Primary Route Network (these are the roads which are green-signed and which we mark as highway=trunk in the UK). I've done spot checks on the spreadsheet and it seems to be an ideal level of detail for cross-checking to make sure we have the Network right. Interesting, many motorways are listed. I wonder if any small stretches of motorways aren't...

I haven't yet, though, used it to alter anything in OSM, as I'm not sure if this would be ok copyrightwise. I don't intend to copy it systemically out, but to use it discover errors and missing bits in our database. So I've written back asking for specific permission to do this.

I also asked if there was a centralised list of classified roads. Apparently there is not - this is handled by the Government Office Regions in England (and I guess by the Scottish and Welsh Governments). Maybe this explains the duplicate A594s!