[talk-au] Road classification in AUS

Tue Jul 23 12:05:50 UTC 2019

Forwarding this email to the list, as it was held in moderation due to the
embedded images.

---------- Forwarded message ---------
From: Andrew Harvey <andrew.harvey4 at gmail.com>
Date: Tue, 23 Jul 2019 at 19:55
Subject: Re: [talk-au] Road classification in AUS
To: Aleksandar Matejevic (E-Search) <v-maalek at microsoft.com>
Cc: talk-au at openstreetmap.org <talk-au at openstreetmap.org>

Thanks for the examples.

On Tue, 23 Jul 2019 at 19:27, Aleksandar Matejevic (E-Search) <
v-maalek at microsoft.com> wrote:

> *Motorway or Trunk: **-38.3999033,145.5370408*
> <https://www.openstreetmap.org/search?query=-38.3999033%2C145.5370408#map=16/-38.4011/145.5388>
>
>
>
>
> Follow this Mapillary.
>
>
> https://www.mapillary.com/app/?lat=-38.39942489999999&lng=145.5372489&z=19.64334424490615&focus=photo&pKey=QjkvLvLb1fNa_SNzVpbcgw
>
>
>
>
> This is [M420], motorway which enters the town. Should the part
> through the town be mapped as trunk or to keep it as motorway, because when
> it leaves town it is for sure motorway but in town it does not fulfill the
> description of motorway, also it has traffic signals.
>

According to the OSM wiki highway=motorway is for a controlled access
highway, which wikipedia says:

"A controlled-access highway provides an unhindered flow of traffic, with
no traffic signals <https://en.wikipedia.org/wiki/Traffic_signals>,
intersections <https://en.wikipedia.org/wiki/Intersection_(road)> or property
access <https://en.wikipedia.org/wiki/Frontage>. They are free of any at-grade
crossings <https://en.wikipedia.org/wiki/At-grade_intersection> with other
roads, railways, or pedestrian paths, which are instead carried by
overpasses <https://en.wikipedia.org/wiki/Overpass> and underpasses
<https://en.wikipedia.org/wiki/Underpass>. Entrances and exits to the
highway are provided at interchanges
<https://en.wikipedia.org/wiki/Interchange_(road)> by slip roads (ramps),
which allow for speed changes between the highway and arterials
<https://en.wikipedia.org/wiki/Arterial_road> and collector roads
<https://en.wikipedia.org/wiki/Collector_road>. On the controlled-access
highway, opposing directions of travel are generally separated by a median
strip <https://en.wikipedia.org/wiki/Median_strip> or central reservation
containing a traffic barrier <https://en.wikipedia.org/wiki/Traffic_barrier> or
grass. Elimination of conflicts with other directions of traffic
dramatically improves safety[1]
<https://en.wikipedia.org/wiki/Controlled-access_highway#cite_note-1> and
capacity."

Based on this, the Bass Highway is trunk not a motorway (it has traffic
lights, roundabouts, it doesn't provide onramp/offramps), so I think you
need to revert your recent tag change to this road, not just for the
sections through towns, but for the whole road.

>
> *Trunk or Primary: **-34.8378323, 138.5029666*
> <https://www.openstreetmap.org/search?query=-34.8378323%2C%20138.5029666#map=18/-34.83795/138.50335>
>
>
> We will follow the [A16] route from junction Victoria Road – Nelson
> Street. These two roads are on the same [A16] route. Victoria Road is
> mapped as Trunk, but Nelson Street is set as Primary Road.
> These both roads look almost the same – two separate ways with two or three
> lanes, no barrier in between:
>
>
>
> *Nelson Street*
>
>
> https://www.mapillary.com/app/?focus=photo&pKey=kJLW93dqu0t4cM34Al4wtA&lat=-34.83935459862475&lng=138.4998110442043&z=17
>
>
>
>
> *Victoria Road*
>
>
>
>
> https://www.mapillary.com/app/?focus=photo&pKey=fqlFms86fTiE-ODwBcrHhQ&lat=-34.83792630649351&lng=138.50419954805196&z=1.8746717329999287
>
>
>
>
> The only difference is road type (Road vs Street). But, route [A16] then
> continues in Semaphore Road, which also looks exactly the same as
> previous two roads, but it is mapped as Primary Road. This street to me
> also looks as trunk. Part of Semaphore Road which is not on [A16] route is
> mapped as *secondary*, but it looks like a *primary* road. In this
> case, should Semaphore Road be mapped as trunk – primary, instead of
> primary – secondary?
>

It's not just the physical condition of the road, but also how important
that road is from the road network perspective, so generally the more
traffic the road gets and the more "important" it is in terms of linking
major centres together, then the higher the classification. So in that way,
two roads which look the same can have different classification based on
their importance in the road network.

>
>
> Next case, on [A16] route, *Causeway Road* is definitely a primary road.
>
>
>
>
>
> https://openstreetcam.org/details/1341011/254/track-info
>
>
>
> Further on, [A16] continues to *Bower Road*, which looks like a trunk
> road, but it’s mapped as a primary.
>
>
>
>
> https://www.mapillary.com/app/?focus=photo&pKey=_jlpimXN_-a17Mt8E92wRg&lat=-34.852086664809406&lng=138.49658016539593&z=17
>
>
>
>
> These all roads are on the same [A16] route.
>
>
>
> If we compare what is written here
> https://wiki.openstreetmap.org/wiki/Key:highway with M, A, B, C routes
> then we find that A route, in most cases, primarily consists of trunks.
> Putting Causeway Road on a side, all other mentioned roads look the same,
> but only one of them is mapped as trunk. Should all of them be turned into
> trunks? If yes, what to do with Causeway Road? Turn it into trunk because
> of A route or leave it as is?
>

I would ignore the A, B, C etc. classification, and instead map based on
the road importance within the network. Indeed that's exactly how
https://wiki.openstreetmap.org/wiki/Key:highway describes the tag values as
different levels of importance within the road network in connecting places.

I wouldn't concern myself too much with what official data says, nor with
the ref numbers, instead go with local knowledge of the road importance.
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