I have two cases where I wonder where the roundabouts are tagged correctly. So far the reference I have on the matter is there, but some cases aren’t covered.
The first case is a roundabout connecting a motorway_link, a secondary road and two unclassified roads (one of them being prohibited to motor traffic). Both the motorway and the secondary road end there, so technically according to the wiki the correct way would be to use unclassified roundabout, but as a lot of trafic will go through from the motorway to the secondary road and vice-versa, this feels wrong. I still left it tagged it secondary, hopefully doing the right thing.
The second case is a roundabout in the middle of a trunk road, connectig two branches of a tertiary road. The roundabout is currently tagged “trunk”, which is correct because the trunk road passes through, however non-motorized trafic such as bikes are authorized to take this roundabout if they stay on the tertiary road ! This makes the mapping subject to confusion as having the roundabout marked as “trunk” may make routing software thinks we can’t bike on the roundabout, but we can.
I’ve never considered those hard rules to be very productive. The highway type should be determined the same way it is for any other highway: according to its importance and construction (and possibly management). I agree with you that highway=secondary makes sense for your example, even though this may deviate from what the article defines as “correct”.
It should be pretty simple to fix this by adding bicycle=yes or bicycle=designated, as appropriate.
Interesting, the case is similar but the big difference is that there is signs marking the end of trunk before the roundabout, and another sign marking the start of trunk agin when exiting the roundabout.
In Châtel-Saint-Denis there is only a sign showing the start of a trunk when exiting the roundabout (in both directions), but no sign showing end of trunk from either directions. I witnessed this first had and fortunately, someone updated pics on mapilary, so you guys can also explore this place from a distance; picture quality seems poor however.
Maybe a difference in traffic law. It might be that a roundabout is a separate way. And that each way needs to be separately marked as a trunk road. So leaving out the sign would already have the desired effect.
What would be interesting here is having Mapillary images entering the roundabout from the side roads (Route de Montreux). If there are trunk signs when entering the roundabout from side roads, then the roundabout is trunk, otherwise not.
I’m 99.9% certain there’s no such sign. If there was, bycicling on the roundabout would be prohibited, but it is allowed.
[Maybe a difference in traffic law.](Maybe a difference in traffic law.)
Sure, it is also possible that this roundabout is not following swiss law. I honestly don’t know much about road law so I can’t comment, but I’m fairly certain some situations on the ground which are outside of legal norms (which are strict and sometimes absurd) have happened and continues to happen in my country.
I just thought about something, since there is obstacles in all 4 directions separating the roads in two it might be possible to tag the roundabout so that two quarters of it are “tertiary” (when following “route de Montreux”) and two quarter of it are “trunk” (when following the trunk road), even though this tagging might be exotic and could potentially confuse renderers and/or routers.