As someone who learnt the consensus about highway tagging in Scotland the hard way, are these changes to roads tagged highway=primary and highway=trunk appropriate? They change the extent of the roads tagged highway=trunk to the point where their trunk status officially ends unlike before where it was tagged as ending on lesser roads. I added sourcing to the roads affected by the first changeset listed. Something similar happened before to motorways in England where a user moved the starting/ending point of motorways to where they were signed as starting/ending and not the point where a lesser road meets/diverges from the motorway. IIRC, there was consensus for the latter considering that the extent of motorways in England have been largely reverted to how they were before the changes were made. Iâm unsure about the consensus in Scotland about road tagging so Iâd like to see what the community thinks about the changes since they affect major roads.
Reality is always very murky. We donât always tag things exactly as they should. For example a village of 300 people might be a town officially but we would tag it as a village. So I donât believe the exact trunk tagging need to apply to the exact length of the motorway and it could also be slightly extended to better facilitate navigation for the router. The first changeset you listed showed a disconnection between the two trunk roads, I think that little piece should be tagged as trunk as well even though itâs not part of the motorway.
Disclaimer: I know next to nothing about motorways.
Legally, motorway regulations begin when one passes a start of motorway sign (bridge over dual carriageway, colloquially âchopsticksâ) and end when one passes an end of motorway sign (bridge over dual carriageway, struck through with a red diagonal line). AFAIK, motorways are mapped on OSM as starting at the point of divergence from a lesser road and the point of convergence with a lesser road. A few rare exceptions occur where the start or end motorway sign is set back significantly from the point of convergence or divergence, e.g. junction 30 of the M25. I believe the same procedure is applied to the start or end of lesser roads like trunk roads, primary roads and secondary roads. Since the start or end of lesser roads arenât as clearly signed as motorways, OSM maps them like motorways. In Scotland, trunk roads function similarly to motorways and have a defined legal point where they start and where they end. However, this is not represented by signage on the ground because they have no regulations which prohibit certain modes of transport like motorways. Personally, I disagree with the rare exceptions to the rule laid out above for the sake of easier navigation, but I believe thereâs consensus for them to be mapped that way. However, with the trunk and primary road changes I outlined above, thereâs no consensus for this and editors like myself have been reverted before for changing the classification of highways around Edinburgh. I believe there should be discussion before further changes are made to the trunk and primary roads in question.
Hi and thanks to @yasslay for raising this discussion topic.
Usually, trunk roads do end at an intersection with more minor roads. Sometimes they do not as in the cases here. In these cases, I think that mapping the reality also improves navigation.
For example, in the case of the A90/M90/A9000 at Scotstoun, the beginning of the start of the trunk section of the A90 being some way to the east appears to be a result of the A9000 merging with the A90 at a location east of the deviation of the M90 away to the south. This ensures that there is at least a small section of trunk road after the merging of the two trunk roads A90 and A9000. Merging two trunk roads to create a non-trunk doesnât make a whole lot of sense in terms of the road hierarchy. Having them merge and then downgrade later makes a little more sense.
In the case of Gogar roundabout and the A720, the roundabout itself is non-trunk as is the last few hundred metres of the A720. This avoids a local journey from A8-South Gyle having a pointlessly brief trunk section.
I understand and agree with your reasoning, however, if we sacrifice some accuracy, I believe extending the trunk section of the A90 east of Queensferry to the fork junction near Mansion Hill and the A720 north of Hermiston Gait to Gogar Roundabout without classifying the roundabout as trunk (see how M8 ends at Hermiston Gait) would be better looking, make navigation easier and reflect the situation on the ground better. That being said, Iâm fine with how the trunk roads are mapped at the moment since theyâre an accurate representation of the legal extent of the trunk roads.
Itâs worth clarifying that a âtrunk roadâ in the UK (a road part of the strategic road network and maintained by a national government body, not a local council) isnât the same as a âprimary routeâ in the UK (a road with primary status as designated by green-backed direction signs). While a primary route may be a trunk road, there are numerous primary routes out there that arenât trunk.
While it does appear that pretty much all Scottish primary routes are trunk roads, perhaps it makes sense to simply tag these roads as being operated by Transport Scotland (thus indicating their status as a designated trunk route by the Scottish government) and then determine what their highway tag should be depending on whether the signage is green/white or white/black (primary and non-primary)?
(For clarification, a primary route is mapped in OSM as âhighway=trunkâ and a non-primary route is mapped as âhighway=primaryâ. Confusing but thatâs how it is.)
The reason Scottish trunk roads in OSM match the TS trunk road list is because some A roads roads have contradictory / outdated signage along their route, so it was thought best to defer to the TS list for consistency.