India route shields

[1ec5]

India has a system of distinctive route shields for national highways and state highways.

It isn’t currently possible to render route shields for any of these routes because the refs include redundant prefixes like “NH” and “SH”. The prefixes are incorrect, because they shouldn’t appear as part of the main legend on the shield, and they aren’t part of the route’s numeric name. (No one would say “State Highway SH14”.)

Another problem is that there are two tagging schemes for national highways: some are tagged network=IN:NH while others are tagged network=IN:NH:<state>, qualified by a two-letter state code. I think some mappers are confused about the network syntax. They’re attempting to incorporate a hierarchy of administrative regions into the value, even though the national highway network is uniformly signposted and numbered throughout the country. I’d suggest only rendering IN:NH and discarding the state-qualified values. State-qualified values are only appropriate for state highways, which are designated independently in each state.

Here’s a background image to use for national highways:

[claysmalley]

At least one National Highway has a 5-character ref:

[1ec5]

Another problem is that there are two tagging schemes for national highways: some are tagged network=IN:NH while others are tagged network=IN:NH:<state>, qualified by a two-letter state code.

A mapper in the OpenStreetMap India Telegram chat explained that network=IN:NH was the older tag, but after the Ministry of Road Transport and Highways began renumbering national highways in 2016, they used different network values for the new numbers, leaving IN:NH as the tag for historic national route relations. IN:NH is also used on superrelations representing current national highways that cross state boundaries, but superrelations are irrelevant to this project since OpenMapTiles ignores them.

The new values contain state abbreviations because they wanted to be able to compare OSM’s coverage of national highways with official and commercial sources and break down the statistics by state. So the overly complicated network values are a shortcut to avoid having to add an area filter to Overpass queries.

[1ec5]

A mapper in the OpenStreetMap India Telegram chat explained that network=IN:NH was the older tag, but after the Ministry of Road Transport and Highways began renumbering national highways in 2016, they used different network values for the new numbers, leaving IN:NH as the tag for historic national route relations.

The historic route relations are tagged with keys other than ref, such as ref:old, so these relations are already being omitted correctly.

The new values contain state abbreviations because they wanted to be able to compare OSM’s coverage of national highways with official and commercial sources and break down the statistics by state. So the overly complicated network values are a shortcut to avoid having to add an area filter to Overpass queries.

In the last couple days, with the consent of the local community, the state-qualified network=IN:NH:* tags have been replaced by network=IN:NH, and the NH prefix has been removed from the ref tags of the relations in this network. The state abbreviations are being moved to is_in:state. Once the tiles are regenerated, we’ll be able to add National Highway and National Expressway shields in short order.

There’s still ongoing discussion about similarly simplifying refs of State Highways and updating the tags on National Expressways. (The SH networks are also state-qualified, but this is correct because the numbering scheme is specific to each state.)

[1ec5]

National Highway shields are yellow while State Highway shields are green:

Sometimes the yellow NH background extends beyond the shield, but I think this is just an artifact of how the signs are manufactured:

National Expressway shields are identical to NH shields except for the “NE” legend and the use of Roman numerals:

In OSM, the relation refs contain European numerals. I suppose it would be reasonable to leave them as is, but we could add a special case to format them as Roman numerals. That would also be useful for some autovías in Spain (#654).

[ZeLonewolf]

Even if they always rendered with the rectangular background, I think it would be more consistent with the style to crop them out. I think we should keep the black rim for contrast, even though at least one of the pictures seems to omit it.

[claysmalley]

Currently working on National Highway shields in #675.

I have some clarifying questions that hopefully the Indian OSM community could answer:

1. National Expressways seem to be dually signed (examples above), with a shield like that of National Highways as well as a blue rectangle with white text. Which one would Indian map viewers expect to see: the NH-like shield, or the blue rectangular shield?
2. I found two different designs for State Highway shields on Wikimedia Commons: one with a badge shape similar to the US Route shield, and another that's just a recolored National Highway shield. In street-level imagery, I can find plenty of examples of the first design, but not the second. Is this an older design that's being gradually replaced? Or is it present in some states but not others? Or is it just an invention of Wikipedians?
3. Major District Roads have numbers, but I can't find examples of signage. Are MDR numbers signed on the ground? If so, what does the signage look like? (Photos would be helpful)
4. According to Wikipedia, Puducherry has RC Routes instead of State Highways. What does RC stand for? Do these have a different shield? If so, what does it look like? (Photos would be helpful)

[1ec5]

National Expressways seem to be dually signed (examples above), with a shield like that of National Highways as well as a blue rectangle with white text. Which one would Indian map viewers expect to see: the NH-like shield, or the blue rectangular shield?

A lot of expressways have something akin to a street name sign attached to gantry signs, but I don’t think this is equivalent to a shield.

I found two different designs for State Highway shields on Wikimedia Commons: one with a badge shape similar to the US Route shield, and another that's just a recolored National Highway shield. In street-level imagery, I can find plenty of examples of the first design, but not the second. Is this an older design that's being gradually replaced? Or is it present in some states but not others? Or is it just an invention of Wikipedians?

I was unsure about both shields actually. I do see the all-green shield on signs that don’t include a number, such as in the first photo in https://github.com/ZeLonewolf/openstreetmap-americana/issues/225#issuecomment-1375220601.

[1ec5]

According to Wikipedia, Puducherry has RC Routes instead of State Highways. What does RC stand for? Do these have a different shield? If so, what does it look like? (Photos would be helpful)

I haven’t come across any photos of shields per se, but the “RC” prefix does appear on street name signs and milestones (in the same manner as for National Highways):

By the way, “RC” is “ஆர்சி” in Tamil, but this translation doesn’t seem to appear on any road signs in photos I’ve come across.

[claysmalley]

By the way, “RC” is “ஆர்சி” in Tamil

This transliterates to "ārsī". Looks like a phonetic borrowing of "RC".