[Talk-us] US Trunk road tagging

[Minh Nguyen]

Vào lúc 21:41 2021-05-05, Adam Franco đã viết:
> At this point I'm thinking of the 
> highway=trunk,primary,secondary,tertiary,unclassified,residential values 
> as simply funny labels for descending numerical values of 
> connectivity-importance. I'm now on board with the position that only 
> motorway implies any physical characteristics.

Whoever came up with the original admin_level=* framework was brilliant: 
by starting out using only even numeric values, it became possible for 
some regions to slot in odd values, ensuring a rough consistency across 
regions while accommodating important distinctions peculiar to a 
particular region. If the admin_level=7 slot weren't waiting to be used, 
I don't know what Ohio and Indiana would've done about townships.

That said, we know from the many discussions over the years about census 
and electoral boundaries that a single hierarchy isn't flexible enough 
for OSM's diverse use cases. admin_level=* works in part because the key 
is secondary to the boundary=* key that indicates the nature of the 
boundary. With highway=*, we have only a single hierarchy, so we argue 
about whether it should be based on functional or physical 
characteristics or some arbitrary mishmash of both. A more complete 
analogy for roads would be, for example, highway=road road_level=4 
access_control=limited.

Some of the use cases I mentioned in [1] would need to avoid a 
hypothetical road_level=* key in favor of something else, some 
combination of expressway=* or access_control=*, width=*, maxspeed=*, 
and highway=motorway_junction (which, after all, isn't limited to 
motorways). That's fine, but it would place a premium on complete 
coverage of these tags, on top of all the work it would be required to 
migrate existing data, editors, and data consumers off of the current 
highway=* keywords. All told, it would be the most ambitious, invasive 
change we make to OSM since the license changeover. Are we stuck between 
that and endless trunk debates, or are there other solutions?

[1] https://lists.openstreetmap.org/pipermail/talk-us/2021-May/021023.html

-- 
minh at nguyen.cincinnati.oh.us