[Talk-us] Trunk

Bradley White theangrytomato at gmail.com
Sat Oct 14 17:23:39 UTC 2017

> The concept of expressway and freeway are reasonably well known concepts;
> it makes a lot of sense to map trunk and motorway to those concepts.

I agree with freeways but not with expressways. I have no data to back
this claim up, but I'm fairly convinced that, while the average
citizen could easily differentiate between "freeway" and "not
freeway", they would be hard pressed to do the same with an
expressway. Anecdotal, but even when I spent time in the Santa Clara
area which has a robust expressway system, I never heard a single
person say "and then get on the expressway...", or even the word
'expressway' mentioned outside of it being the suffix of a road name.
You're right that it's not a terribly difficult concept to understand
and thus map, but I disagree that it's an important concept in
explaining the road hierarchy in the US, so much so that we can equate
an entire class of importance with them. We have a robust, clearly
signposted freeway network in the US. We do not have the same with
expressways. Roads tend to go in and out of "expressway" qualification
depending on context, traffic levels of connecting roads, and highway
budget & design policy. A road being built as an expressway is
suggestive of its importance at best, and certainly not indicative.

Edmonton has many roads around the east and west of the downtown area
that are clearly built as expressways. However, they are only tagged
secondary because, fundamentally, you only really need to use them to
get around the immediate vicinity. Despite being very high quality
roads, they aren't all that important in the grand scheme. I can point
to many examples of urban roads that likely meet an expressway
definition in my current home city of Reno, including one under
construction. It would be absurd to me to tag them as being second in
importance only to motorways just because they are well-built roads,
because they're unimportant outside of getting around the relatively
small Reno-Sparks metropolitan area.

The "highway" key is about importance. The only category we have
full-stop made equivalent with a type of road design is "motorway".
>From trunk on down, it is just different grades of importance. These
are how the definitions are listed on the 'Key:highway' page, which I
consider to be definitive. The fact that the words "trunk", "primary",
"secondary", ... are used is an artifact of the UK roots of OSM. Had
this project started in the US, the keys would probably be "freeway",
"principal_artery", "major_artery", "minor_artery", "major_collector",
... leaving UK users scratching their heads trying to figure out how
to adapt these definitions to their own network. In countries with
signposted expressway systems, it is meaningful in understanding the
road network to equate trunk with expressway, so they do that. I don't
think doing the same is meaningful in the U.S. given how much
variability and inconsistency there is with how and where expressways
are constructed.

> Even a lot of renderers make this same assumption:  mkgmap maps trunk to
> Garmin's concept of expressway and motorway to freeway.  Osmand, easily the
> most popular data consumer for OpenStreetMap, makes the same assumption (to
> the point that most of it's map painting styles, the only differentiation
> between trunk and motorway is a color pallette shift).  It really wouldn't
> hurt the US community to have a "come to Jesus" moment on this,
> particularly when using the MUTCD definitions for expressway and freeway as
> qualifiers for trunk and freeway, makes this relatively easy.  The
> corollary to "don't tag for the renderer" is "don't break the renderer".
> Highways without access control being excluded from trunk or motorway isn't
> an intrinsically bad assumption to make.  Especially if we come to
> agreement on that, we can start having a productive talk on how to make
> carto not suck for Americans without breaking it for everyone else.

I'm really not that concerned with how third-party applications decide
to paint their roads. It's up to them to work with the data we
provide, not the other way around. If it is important to Garmin or
other applications to translate expressways, this can usually be
deduced from other tags, or we can trivially add an "expressway=" tag.
I also disagree that the carto in the US is bad, other than our
insistence that two-lane are categorically not trunk leaving
meaningless splatters of orange around the map at low zoom.

Also, apologies ahead of time if I keep breaking the archive
hierarchy, I'm not totally familiar with how to drive a mailing list
and I have yet to find a guide online that explains how.

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