[Talk-us] Trunk

Nathan Mills nathan at nwacg.net
Sat Oct 14 19:53:47 UTC 2017


I think I've said this before, but I'm mostly in agreement with Paul's position. Trunk should apply to divided, limited but not controlled access highways. Other uses should be exceptions in the same vein as rural interstates with a few at-grade intersections keeping their motorway status.

Expressways may often not be of more than local importance, though they often are. US 412 in Arkansas is an example which should be part trunk part primary, IMO. Even when they are of only local importance, they should still get the trunk tag, same as a short motorway still being a motorway despite being completely irrelevant to the overall national road network.

Road maps in the US have long differentiated between freeway/expressway and has had both of those clearly different than US and state highways we'd be tagging as primary. Map users expect to see expressways shown differently. We have the tag, it already renders more like motorway in a similar style to other maps, so it makes sense to me to work like other maps since it's what end users expect. Given that the tag is already there and is fit for purpose. Unless someone can show me a situation in which critical information can't be conveyed if an important, but undivided, road is tagged primary rather than trunk (Assuming the undivided section is not a short interruption in an otherwise continuous expressway) I just don't see the benefit of using it to mean "more important than primary" rather than "divided but not fully access controlled"

In short, both maps and common use in the US have historically had three main classes of paved road. Freeways/motorways, expressways/trunks, and everything else. The visual difference between the lower class roads was either based on network importance or whether it is a US or state highway, but the higher class (faster) roads have long been classified apart from everything else in a way that maps very well to motorway/trunk as it has generally used by most US mappers aside from NE2 thus far.

It's less work on so many levels also. Creating a new tag requires significant work on the render side, but doesn't really gain us much over just using primary for roads that some think are important enough to be a trunk but are undivided. The wiki definition for primary is already "the most important non-motorway route between two cities" (essentially, and ignoring the variation in use between rural and urban areas) I don't think any backend work is worth the insignificant increase in expressiveness of the map we'd get from using trunk as a better primary and introducing a separate tag to denote an expressway.

As far as Alaska goes, it's different enough I don't think it's at all unreasonable to adjust the rules a bit there, just like there is already some variation between states and countries on how to differentiate between primary/secondary/etc.

If the issue is the low zoom rendering of short trunk and motorway segments, that's a misfeature in carto, not a tagging issue. And not even so hard to fix now that route relations are so prevalent.

-Nathan


On October 14, 2017 1:23:39 PM EDT, Bradley White <theangrytomato at gmail.com> wrote:
>> 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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-- 
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