[Talk-ca] Proposed changes to road classification and related stuff

[Adam Franco]

Hello from a neighbor just south of your border! The wiki page at United
States/2021 Highway Classification Guidance
<https://wiki.openstreetmap.org/wiki/United_States/2021_Highway_Classification_Guidance>
provides an overview of the changes we're making to highway classification
in the US.

Regarding the highway=trunk tag -- this has historically in the US (and
Canada to some extent) been used to mean "expressway construction, but not
quite motorway" rather than being a network-importance signifier as it is
in the UK highway system that OSM is based on.

This  trunk == expressway way of tagging causes two problems:

   1. No way to identify high importance, long distance roads that are of
   two-lane construction.
   2. No way to filter out urban expressways at low zooms. Cities become a
   smear of roads.

When followed rigorously, this older trunk == expressway way of tagging has
had the unfortunate effect of leaving no way to identify high importance
roads that should be shown on continent-scale maps when those roads are
built as two-lane highways with at-grade intersections. This has left
low-zoom maps of the US with a patchwork of roads around cities and big
gaps in between.

The second problem with the trunk == expressway way of tagging comes when
urban expressways are *also* tagged with highway=trunk to indicate their
enhanced infrastructure. This tagging forces renderers to include these
urban expressways at too low of a zoom, making urban areas a smear of
roads. In the US we're shifting to use the expressway=yes tag to indicate
this enhanced infrastructure while leaving the highway=* tag to indicate
network importance. Thus, an urban expressway that connects between suburbs
may be tagged highway=primary+expressway=yes to indicate both its more
local network importance as well as its enhanced infrastructure.

In general, Canadian tagging is starting from a much closer alignment to
this new US-specific guidance than our own tagging is. Canada has many
examples of two-lane highways that connect long distances through
sparsely-populated areas. Many of these two-lane Canadian highways (for
example, Ontario Highway 11 <https://www.openstreetmap.org/relation/5501463>)
are currently tagged highway=trunk in a way that aligns with the
network-importance scheme. Still, there are a number of cases where
important regional connections aren't tagged highway=trunk yet or where
less-important urban expressways are still tagged as highway=trunk.

One example that should likely be fixed is Route 133
<https://www.openstreetmap.org/#map=13/45.0807/-73.0971> between the
not-yet-completed Autoroute 35 and Vermont's I-89. It is currently tagged
as highway=primary in its two/three-lane section and highway=trunk in its
expressway section. Given this road is a non-motorway connection between
two motorways and connects Montreal to Burlington & Boston it would likely
have a "trunk" importance in the network.

Best,
Adam

On Tue, Feb 8, 2022 at 9:36 AM Martin Chalifoux via Talk-ca <
talk-ca at openstreetmap.org> wrote:

> I feel the same as you do John, and I also like the way it is right now.
> So I would like to understand the issues they want to fix and I don’t get
> it yet. As the saying goes, it if aint broken don’t fix it.
>
> On Feb 8, 2022, at 09:28, john whelan <jwhelan0112 at gmail.com> wrote:
>
> I suspect it all stems from the roots of OSM.  A UK motorway is quite
> different to a Canadian one and there has been lots of discussion about
> classification of primary, motorway, trunk etc. in various countries.
>
> Personally I quite like the existing tagging and don't really see the need
> to retag everything.
>
> It isn't clear to me what the advantage of retagging everything is.
>
> You loose the sense of local ownership if you move to standardised tagging
> and in this case where it is not black and white I fail to see any
> advantage.
>
> Cheerio John
>
> On Tue, Feb 8, 2022, 09:15 Martin Chalifoux via Talk-ca <
> talk-ca at openstreetmap.org> wrote:
>
>> Hi Miguel, maybe I missed something, what is the issue with the trunk
>> designation to start with ? What is broken that you want to fix ? You seem
>> to want to avoid the trunk tag altogether and move everything up to
>> motorway or down to primary as if trunk was improper.
>>
>>
>>
>> _______________________________________________
>> Talk-ca mailing list
>> Talk-ca at openstreetmap.org
>> https://lists.openstreetmap.org/listinfo/talk-ca
>>
>
> _______________________________________________
> Talk-ca mailing list
> Talk-ca at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk-ca
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk-ca/attachments/20220208/e64a5476/attachment-0001.htm>