[Talk-us] US Trunk road tagging

[Paul Johnson]

On Tue, May 4, 2021 at 10:31 PM Bradley White <theangrytomato at gmail.com> wrote:
> Here are some counterpoints as to why I'm not completely on board with
> "importance" tagging yet:
>
> The issue of floating "trunk" segments on the main slippy map is
> awful, agreed.

Aesthetics aside, such floating chunks does reflect the ground truth.
It's not OSM's fault that highway departments, especially in rural
parts of the country, prefer grand islands of expressway to nowhere.
We just document it.

> However, I think this is at least in part a
> cartographical compromise rather than a data/categorization problem. I
> think a US-oriented map styling that weighs US/state route
> designations more heavily than OSM classifications when deciding
> rending prominence would result in much less arguing about this.

Which, thankfully, is already reasonably attainable by rendering based
of network tags of road route relations.

> I also worry that adopting a strictly "importance"-based definition
> for trunk roads will induce an over-zealous use of 'motorway', a
> problem the US already has (trying to tag every single time a divided
> road has any kind of grade separation as 'motorway' is bad tagging,
> but prevalent around the US).
>
> I think the fact that so many US mappers
> are so eager to tag every singular divided grade-separated interchange
> as 'motorway' (regardless of what comes before or after the
> interchange) speaks to the fact that many mappers expect to see a
> rendering distinction between a plain-old highway and a more
> freeway-like road. Removing an in-between category will exacerbate
> poor use of the 'motorway' tag, unless stricter guidelines are put in
> place for 'motorway' use in tandem.

This is particularly prominent on stretches of interstate highways
that aren't really freeway but signed as interstates.  Between the
international border and the last exit before the border on both ends
of Interstate 5 come to mind as "not a freeway but is an interstate".
There's also decent length chunks of interstates that are not
freeways, with multiple intersections in a row in the desert west
(even if they are dual carriageway and fast, and most of the
crossroads get about the same traffic annually as my driveway, they
have at-grade intersections).

> This is the crux of the argument to me: is a road being constructed to
> an "expressway" standard significant enough to bestow its own
> classification in the importance hierarchy?
> I'm *slightly* more convinced that the answer is yes. If we accept
> freeways as being, strictly by physical construction & with no regard
> to the importance of the route they carry, important enough to warrant
> its own class, then I don't think it's a big stretch to have another
> category just beneath it for roads a layperson might call a freeway,
> but that a roads geek knows is not. I certainly know of some freeways
> that are nowhere near important enough to need rendering on low zoom,
> but it's a compromise we accept.

I think it might also be time to consider formally introducing lower
classes of roads.  Quaternary, quintenary, etc; this would help with
borderline absurd situations like the ~10-network (in addition to US
and interstate) Texas state highway system.