[OSM-talk] A new highway tagging scheme

Cameron Patrick cameron at patrick.wattle.id.au
Mon Aug 27 02:39:25 BST 2007

Andrew MacKinnon wrote:

> I think that our current highway tagging scheme is too limited. The trunk,
> primary, secondary and tertiary road types are loosely mapped to
> administrative classifications, but they are also linked to the physical
> state and the "importance" of the road. Administrative classifications
> frequently have little to do with the importance or the quality of the road.

My interpretation of the OSM highway= tag has been "how important is
this road for through traffic" rather than physical or administrative
status.  As you say, in many countries, the latter is largely

Most of the physical distinctions we already have tagging schemes for.

> - Two_lane_motorway - a controlled-access highway with slip roads but only
> one lane in each direction, and generally no median. Also known as a
> "super-two".

highway=motorway lanes=1 (if this really is important to distinguish)

> - Dual_carriageway - a non-controlled access road (trunk road, arterial
> road, etc.) with a median in the centre

Currently tagged by two parallel ways with oneway=yes.

> - Multi_lane - a non-controlled access road (arterial road, etc.) with no
> median in the centre. Centre islands may exist at intersections.
> - Two_lane - a paved road with two lanes, one in each direction, and a
> painted line in the centre. One way roads with 2 or more lanes, which do not
> form part of a motorway or dual carriageway, should be tagged two_lane.

We already have a lanes= tag for situations where this is useful.

> - Track - An unpaved road which is not covered with gravel, and/or which is
> only suitable for 4WD vehicles.

If we're going to do this, there's probably a good case for
distinguishing "dirt roads in good condition", "dirt roads easily
navigable in a 4WD" (noting that 'a 4WD' encompasses a wide range of
vehicles), "tracks which require some research before attempting".
Obviously, for many roads, this also varies seasonally (e.g. floods in
the wet season can make much of northern Australia inaccessible except
by helicopter) and/or the condition decays with gradual neglect.

Again, we have a surface=unpaved tag already.

> - National - administered by the national government. If roads are assigned
> a national numbering or naming scheme scheme, but maintained by regional
> authorities (e.g. US highways, interstates and the Canadian Trans-Canada
> Highway), they are tagged as national.
> - Regional - administered by the regional government (e.g. state or
> province).

Hmm.  In Australia we have the interesting situation of interstate roads
which are nationally funded but regionally administered.  I understand
that the USA is similar.  Anyway, that's just nitpicking.

Often the administrative classification of a road is unclear / not signposted.

> * Admin_type - provides information about a road's administrative class, if
> multiple classifications exist. This is not needed for motorways, if they
> are tagged as highway=motorway or highway=two_lane_motorway, and primary
> two-lane highways, if tagged as highway=two_lane or
> highway=dual_carriageway.
> - Motorway - Legally classified as a motorway. May not actually be a
> motorway in certain sections.
> - Trunk - In the UK, a one- or two-digit A road.
> - Primary - Legally classified as a primary road - e.g. A roads, primary
> provincial/state highways
> - Secondary - Legally classified as a secondary road - e.g. B roads,
> secondary provincial highways
> - Tertiary - Legally classified as a tertiary road - e.g. C roads, tertiary
> provincial highways

Again, as far as I know, there's no obvious way where I am to determine
the legal classification of a road as trunk/primary/secondary/etc from
any signage on the road itself.


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