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SR for state roads

I propose that we standardize on tagging ways carrying Indiana state roads with ref=SR * rather than ref=IN *. The network=US:IN tag in route relations would remain unchanged.

The status quo is a mix of both "SR" and "IN". Back in 2011 or so, NE2 tagged the vast majority of ways carrying Indiana state roads with ref=SR *. I did likewise to many state roads in southeastern Indiana. Some time later, a majority of these roads were retagged ref=IN *, but this retagging was performed haphazardly: many routes wound up switching back and forth between "SR" and "IN" several times within even the same county. Most bridges and highway exit ramp destinations have retained ref=SR * and destination:ref=SR *, respectively. As of 2014, 65% of ways were tagged "IN" compared to 35% tagged "SR". [1] By July of this year, the proportion of "IN" tags reached 91%. [2]

Over the years, I had quietly maintained "SR" usage in the southeastern corner of the state, where I regularly map. But yesterday, in 65522868 (achavi, OSMLab), I started retagging routes' ways to be more consistent, focusing on routes that alternated between the two prefixes and any routes that had concurrencies with them. Before I knew it, I had retagged a large number of routes throughout the state. Now only 63% of ways are tagged "IN", compared to 37% tagged "SR", close to the level in 2014. [3] Since I wound up making a much larger change than expected, and because there was more inconsistency than I had imagined, I feel the need to start a conversation with other Indiana mappers about standardizing these refs.

As far as I can tell, the main argument for ref=IN * is that map renderers can choose a shield based on the prefix of each way's ref=* tag. The postal abbreviations are unique and unambiguous. (However, this is only the case within the U.S., discounting county roads bearing the same "CO" prefix as Colorado state highways.) Since a number of states refer to their routes using postal abbreviations, putting postal abbreviations in the tag is seen as promoting data consistency. But note that there isn't a national rule about using postal abbreviations: among Indiana's neighbors, Ohio consistently uses "SR" and Michigan consistently uses "M". (Illinois and Kentucky use postal abbreviations because that's how people actually refer to state highways there, this Indiana sign notwithstanding.)

The main argument for ref=SR *, meanwhile, is the on the ground rule. Although the white, rectangular state road shields are posted at most major junctions in Indiana, there are still many contexts in which a sign or document must refer to a state road in plain text. In these contexts, "SR" is used almost exclusively. In my opinion, these are the contexts that should determine what we use in the ref=* tag on ways. I compiled the following sample of Mapillary images showing "SR" used as an abbreviation on street name signs, but I'm sure there are other examples on distance signs and variable-message signs.

Ohio also uses "SR", but it isn't necessarily a problem that two neighboring states would use the same prefix. Map renderers have two options for disambiguating:

Interested to hear the opinions of other Indiana mappers.

 – Minh Nguyễn 💬 09:05, 17 December 2018 (UTC)

I don't edit often in Indiana, but I figure I'd chime in for what it's worth. This would probably do better in the talk-us mailing list. These wiki talk pages don't seem to often get much attention.
I think that the abbreviation in ref should be what is commonly officially used in the state. For Indiana's case, this seems to be SR. Wikipedia uses this convention and abbreviates such state routes with SR.
Renderers really should be using route relations and not trying to decipher the dozens of ref tag abbreviations. Honestly, keeping ref around on ways seems more like the only generally approved tagging for the renderer (i.e. Carto/Mapnik) than anything else. --Roadsguy (talk) 01:38, 8 January 2019 (UTC)
Other than a few remaining bridges and some old_ref=* tags, virtually all the refs have been switched over to SR *, thanks to a couple other mappers who specialize in Indiana. I'm glad non-renderers, such as navigation software, can now rely on ref=* in this state to reflect the real-world plain-text usage, just like with name=*. – Minh Nguyễn 💬 05:34, 11 September 2020 (UTC)