[OSM-talk] A new highway tagging scheme

Andrew MacKinnon andrewpmk at gmail.com
Sun Aug 26 23:03:51 BST 2007


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.
For example, sections of certain motorways (like Autoroute 20 west of
Montreal, Quebec, Canada) have traffic lights and intersections, but they
are still officially classified as motorways.

For this reason, I propose a new tagging scheme which separates the physical
quality of a road and its administrative status. It replaces the current
highway tag with two tags, a tag which reflects the highway's quality of
construction and one which displays its official administrative status.
Currently, footpaths, cyclepaths and bridleways will be unaffected by this
reform. Here is an example of how it could work:

* Highway tag - provides basic information about the type of road (ignoring
all administrative classifications)

- Motorway (existing) - a controlled-access highway with at least two lanes
in each direction
- Motorway_link (existing) - a slip road
- 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".
- Dual_carriageway - a non-controlled access road (trunk road, arterial
road, etc.) with a median in the centre
- 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.
- Minor - Any road currently tagged highway=residential or
highway=unclassified. A road, whether paved or unpaved, wide enough for two
cars to pass, with no painted line in the centre. If it is one way, the road
should be wide enough for two cars to fit side-by-side.
- Narrow - Any road, paved or unpaved, not wide enough for two cars to fit
side-by-side; in urban areas, these are generally one-way streets. In rural
areas, traffic in both directions is often allowed.
- Track - An unpaved road which is not covered with gravel, and/or which is
only suitable for 4WD vehicles.

Note that there are no direct equivalents to primary, secondary, or tertiary
here. These tags will be gradually retired, replaced with the new tagging
scheme, because they do not provide enough information. It may be possible
to use a script to convert primary, secondary, tertiary to the new scheme in
an area where these tags have specific, known meanings.

* Administrative tag - provides information about a road's administrative
classification. The specific meaning of these highway tags can be determined
by checking which region a highway is located in. Alternatively, some sort
of jurisdiction tag could be used.
- 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).
- Regional2 - administered by a second level of regional government, if it
exists. In the US and Ontario, Canada, this is used for county roads.
- Local - administered by a municipality or other local authority
- Private - owned by a private landholder. Assumes access=private unless
access=permissive is specified.

* 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

* Additional information - can be provided by existing tags such as
maxspeed, oneway, surface, lanes, width, traffic_lights, stop, etc.
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