[Talk-GB] OSM Road Classification - Trunk/Primary
Barry McGuire
barry86m at gmail.com
Tue Sep 14 19:09:20 UTC 2021
The UK's A and B classification are the original ones that other countries
have tried to emulate.
The trunk road network was started in the 1930s, and became the current
strategic road network (commonly still known as trunk roads):
https://highwaysengland.co.uk/about-us/our-roads/
https://traffic.wales/welsh-government-strategic-road-network-map
https://www.transport.gov.scot/publication/scottish-trunk-road-network-map/
A lot of roads were de-trunked in the 1990s to allow the Highways Agency
etc to concentrate on the nationally important roads that made up their
(strategic) network. The strategic road network is designated by the
respective governments and is a break in importance between nationally
important A roads, and other A roads.
The primary/non-primary distinction was introduced in the 1960s to aid
navigation due to the increase in car ownership (e.g. follow signs to
Bolton, then take the A579 east for 3 miles, then turn left onto Radcliffe
Moor Road). This is why a difference in signage was introduced too. These
days people usually use satnavs so don't use the primary routes as
originally intended for navigation.
Changing the OSM UK definition as proposed would first of all better align
the UK OSM definition with the global OSM definition (trunk = important but
not a motorway) and secondly align UK OSM definition more accurately with
UK terminology (rather than having the strange situation of primary =
non-primary).
Retaining the current system produces the quirks mentioned previously e.g.
primary B roads and routes between primary destinations not being primary,
which are difficult to handle - in fact each of the primary B roads are
designated differently on OSM (one as trunk and one as secondary).
Barry
On Tue, 14 Sept 2021 at 19:30, Tom Hughes <tom at compton.nu> wrote:
> Well the UK definitions are literally the originals and other
> countries have attempted to align their definitions with us to
> some extent though how well that can do that will vary.
>
> I have no idea what the definition of "strategic" is because
> it's a new concept I haven't encountered before.
>
> The primary route network is a defined set of roads that
> connect a specified set of primary destinations - we did
> actually get a not entirely accurate list of the roads that
> make it up via FOI many years ago.
>
> The other big advantage of the primary route network as the
> basis of the definition is, as somebody has said, that it's
> easily detectable on the ground by green/white signage.
>
> Fundamentally it's a deliberate break in importance of the
> roads designated by government and show in signage and recognised
> on basically all UK maps which render primary and non-primary A roads
> differently.
>
> Tom
>
> On 14/09/2021 19:24, Barry McGuire wrote:
> > Even if we neglect the conflicting terminology there are two issues
> > remaining:
> >
> > 1) The OSM definition of trunk (i.e. major roads that fall short of
> > motorway standards) implies a higher level of importance than many of
> > the UK's primary routes.
> > 2) It is exceptionally rare in other countries, particularly in Europe,
> > for towns and cities to have a 'trunk' road running through their
> > centres, whereas it is common on UK OSM.
> >
> > These two issues indicate the threshold of tagging a road as 'trunk' on
> > UK OSM has been set at too low a level and should be raised. The obvious
> > threshold would strategic/non-strategic, which has the added benefit of
> > aligning terminology.
> >
> > Given there is a long history for requests to change, does this not
> > indicate the current approach could be improved? If OSM's aim is to map
> > the world, then shouldn't the mapping standards between countries be as
> > similar as possible?
> >
> > Barry
> >
> > On Tue, 14 Sept 2021 at 18:52, Tom Hughes <tom at compton.nu
> > <mailto:tom at compton.nu>> wrote:
> >
> > Yes it is partially a result of a misunderstanding at the
> > very beginning but actually it worked out well.
> >
> > Whether something is actually trunk is not really that
> > important - whether it is part of the primary route network
> > is really what makes an A road more or less important than
> > another one.
> >
> > There has long been consensus on the tagging, and there is
> > an equally long history of new people turning up and wanting
> > to change it to match the official trunk classification.
> >
> > Please try and forget the words "trunk" and "primary" and
> > just think of them as tokens that mean more/less important.
> >
> > Tom
> >
> > On 14/09/2021 17:50, Barry McGuire wrote:
> > > It's strange that the highway=primary tag is used for non-primary
> > > routes, and it seems like an historical accident caused by people
> > > assuming trunk roads and primary routes are the same thing, when
> > they're
> > > not (usually). Trunk roads form part of the strategic road
> > network and
> > > are managed by a highways authority (e.g. "National Highways"
> > formerly
> > > Highways England, and their relevant counterparts in Wales and
> > > Scotland). Primary routes are selected routes between primary
> > > destinations. Other A roads are roads connecting important
> > (although not
> > > necessarily primary) destinations.
> > >
> > > The Scottish OSM maps already have their strategic routes as
> > trunk, with
> > > all other A roads as primary, which more closely follows OSM
> > terminology.
> > >
> > > In Wales the vast majority of their primary routes are also
> > strategic
> > > (trunk) routes, but not all of them.
> > >
> > > In England there is a proliferation of roads at the OSM 'trunk'
> > level
> > > which isn't seen in most other countries, especially not in town
> and
> > > city centres. Many of the roads are currently tagged as 'trunk'
> > because
> > > they're primary routes but they're single carriageway, when OSM
> > usage
> > > indicates 'trunk' roads are 'high performance or high importance
> > roads
> > > that don't meet the requirement for a motorway'. This implies they
> > > should be mostly dual carriageway and high importance, yet fall
> > short of
> > > motorway classification (e.g. A1, A11, A12, A14, A19, A2, A20,
> > A23, A27,
> > > A30, A31, A34, A35, A38, A4, A47, A66). This further implies that
> > using
> > > the 'strategic route' designation for the 'trunk' tag would be
> more
> > > appropriate than using the 'primary route' designation.
> > >
> > > Proposal to align UK road types with OSM types as follows:
> > > OSM Motorway = UK Motorway
> > > OSM Trunk = UK strategic routes, known as 'trunk' routes
> > (Currently UK
> > > primary A roads)
> > > OSM Primary = All other A roads (Currently UK non-primary A roads)
> > > OSM Secondary = B roads
> > >
> > > Strategic route designations can be found by using data released
> > under
> > > OGLv3, just like the NaPTAN data.
> > >
> > > There are a few edge cases to consider:-
> > > * B5093 Mosley Road, Fallowfield, Manchester is designated as a
> > primary
> > > route and is also a B road. Resolved by changing to strategic =
> > trunk.
> > > * B6261 at Shap, Cumbria linking A6 to M6 is designated as a
> primary
> > > route and is also a B road. Resolved by changing to strategic =
> > trunk.
> > > * A505 and A602 between Stevenage and Luton are not primary routes
> > > despite linking two primary destinations. The proposal would
> > place this
> > > road on the same level as all other A roads, by abolishing the
> > > distinction between 'primary' and 'non-primary' A roads on OSM.
> > >
> > > England-Scotland border (West to East) - 2 changes at the border
> > (A7 and
> > > A68)
> > > * M6 Motorway
> > > * A7 primary route (Scotland strategic, England non-strategic)
> > > * A68 primary route (Scotland strategic, England non-strategic)
> > > * A697 primary route (Scotland non-strategic, England
> non-strategic)
> > > * A1 primary route (Scotland strategic, England strategic)
> > >
> > > England-Wales border (North to South) - 1 change at the border
> (A465)
> > > * A494 primary (Wales strategic, England strategic)
> > > * A55 primary (Wales strategic, England strategic)
> > > * A483 primary (Wales strategic, England strategic)
> > > * A535 primary (Wales non-strategic, England non-strategic)
> > > * A5 primary (Wales strategic, England strategic)
> > > * A483 primary (Wales strategic, England strategic)
> > > * A458 primary (Wales strategic, England strategic)
> > > * A44 primary (Wales non-strategic, England non-strategic)
> > > * A438 primary (Wales non-strategic, England non-strategic)
> > > * A465 primary (Wales strategic, England non-strategic)
> > > * A40 primary (Wales strategic, England strategic)
> > > * A48 primary (Wales non-strategic, England non-strategic)
> > > * M48 motorway
> > > * M4 motorway
> > >
> > > Changes of designation at borders are not unusual, so I'm not
> > concerned
> > > about that.
> > >
> > > The only real downsides to this proposal are the work involved
> > (which
> > > shouldn't really take too long) and the loss of information about
> > which
> > > roads are designed as primary - which is a bit of a false
> > distinction in
> > > any case as primary routes do not indicate the actual standard or
> > > importance of the road, just that they link two 'primary
> locations'.
> > > Note that 'primary' locations do not mean they they're actually
> > > important locations, just that they're useful for navigation
> > purposes
> > > (e.g. Scotch Corner as a junction, and Stevenage for itself and
> the
> > > towns around it). The use of those locations for navigation
> purposes
> > > made sense in the 60s but with satnavs etc the standard and
> relative
> > > importance of the road should take priority on maps.
> > >
> > > Thanks,
> > > Barry
> > >
> > >
> > > _______________________________________________
> > > Talk-GB mailing list
> > > Talk-GB at openstreetmap.org <mailto:Talk-GB at openstreetmap.org>
> > > https://lists.openstreetmap.org/listinfo/talk-gb
> > <https://lists.openstreetmap.org/listinfo/talk-gb>
> > >
> >
> >
> > --
> > Tom Hughes (tom at compton.nu <mailto:tom at compton.nu>)
> > http://compton.nu/ <http://compton.nu/>
> >
>
>
> --
> Tom Hughes (tom at compton.nu)
> http://compton.nu/
>
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