There are three double-deck freeways (motorways) in San Antonio, Texas (I-10 between Frio and Fredericksburg, I-10/I-35 at Alamo, and I-35 between I-10 and I-37). Another mapper erroneously tagged the lower deck of the first as tolled express lanes based on a mistaken assumption, which I reverted, but now we’re debating the relation modeling.
The three upper decks were built to expand capacity in the central area of the city, where the ROW was constrained. In all three cases, neither deck is clearly the “local” or “express” deck (both decks have local exit and entrance ramps), and the overhead signage is based on the succeeding interchanges (many of the decks lead to exit-only ramps once the decks recombine).
My main questions are:
How do I model the relations? (Do I stuff everything in the main relation? Do I create a secondary relation, and which deck do I use for it? Do the secondary relations use the same ref?)
How do I model the signage? (ref? destination:ref?)
Can you share an exact location where we can find such double-deck freeways mapped? I tried (only) “San Antonio, Texas (I-10 between Frio and Fredericksburg)”, that is I think the north-south I-10 in this view but sampling two points I did not see any signs of a double-deck freeway.
To my opinion, relations are no of any importance mapping this, AFAIK these relations are only a way to group all way segments that belong to one freeway and ordering is not that important. Or … are you referring to another type of relation?
Leave it to a (Discourse) noob to forget to link the map. You’re on the right track, though that view only shows the upper level. OpenStreetMap is an example of the I-10 double-deck. It’s actually three carriageways (the lower level, and two viaducts for the upper level). The others are built similarly. The I-10/I-35 segment is at OpenStreetMap , and the I-35 segment running along the north side of downtown is at OpenStreetMap .
And, actually, some people do put value in the route relation ordering. I certainly do. (I’ve done a few changesets before solely to reorder large route relations.)
Interesting piece of infrastructure, One More Lane Bro / One More Lane Will Fix It.
Well, keeping these relations somehow ordered can not do harm, it makes checking easier but indeed the Josm relation editor shows that not that these ways are parallel, see for example relation 2128875.
I do not think it is useful for any data user, but if somebody has evidence on the contrary for that, that would be good to know.
One 2) how to model signage, I do not see what should be special for that, it are just 3 parallel roads that all should be tagged as were there only one road.