[Talk-us] US Trunk road tagging

[Bradley White]

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. 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.

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 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.