Important unpaved roads exist, so needs a reboot

Posted by Mark Newnham on 10 January 2014 in English (English)

Conflicting methodologies

A recent discussion on the osm-dev list highlighted the difficulty in using the main Highway page as a basis for understanding how to map highways outside the core areas where most OSM mappers are found, i.e. Western Europe and the urban areas of other industrialized nations.

The focus of the discussion is primarily the setting up of the Highway Tag Africa page, and objections, based on the assertion that global standards should be defined in the main page, and applied world-wide.

Where theory and practice are incompatible

The problem, however, is that the standards that appear in the main pages are almost exclusively based on the road system in the United Kingdom, a country where every road is paved, well-signed and well-maintained. See for example:

Did you see an unpaved road on those pages? No, you didn't.

Now have a look at This Chart, Even the USA has only 68% paved roads, and for Australia, the number falls to only 38%

Consequences of the current methodology

  1. As the number of unmapped paved roads diminishes in countries with higher proportions of unpaved roads, and mappers turn to mapping smaller roads, confusion ensues when trying to associate the necessary level of highway with the physical state of the road. In the end, too many usable roads are mapped as tracks, making them unavailable for mapping/routing software.
  2. Numerous country-specific sub-pages are spawned, each attempting to shoehorn the standards set out on the main page into a countries road system. see:
  • USA Road Tagging The Page is divided into sections that cover some of the states requirements, each discussed in a separate manner, and the talk page includes unresolved pleas for help going back to 2009
  • International Equivalence In Canada and Brazil, indications are that urban areas follow the guidelines established on the Main Page, but rural areas follow the scheme broadly similar to the Highway Tag Africa proposal. The page itself has entries in numerous languages, making standards comparison impossible.
  • In Australia Road Tagging, the road numbering scheme standard is defined in a government document, which is no longer available at the target URL

A Proposal for a series of standards

  1. The Highway Tag Africa definitions for roads are based on socio-political rather than road-surface/speed/width standards. These can be broadly applied to roads in all Nations. This should be the basis for the Highway page.
  2. The existing Highway page should moved To a Highway_Tag_United_Kingdom and modified accordingly
  3. The numerous pages associated with road standards should be combined/cross-linked
  4. The International Equivalence should be translated to English, and mappers encouraged to provide full translations of the page
  5. A standardized country specific highway template should be designed.
  6. A consistent methodology of linking these pages should be designed, so for mappers who want to understand how to map roads:
  • Go to the highway page to understand the core concepts of highway mapping
  • A link to the international page allows the mapper to find the relevant Nation/Continent. Consistently translated pages allow the mapper to get the correct links
  • A nation/continent page shows the mapper how to apply the global standards at a national level. The goal is to dissuade the mapper from defining standards at a micro/local level
  • For areas with autonomous authorities, such as USA, the highway template can be reapplied at a state level


Mapping of roads is a key portion of a beginners' mapping skills, and an organized, consistent set of documentation is essential in order to avoid needless mistakes and conflicts in methodology. A revisit of the core documentation for this function seems appropriate in light of the ongoing conflicts identified in the opening paragraph of this posting.

Comment from Richard on 10 January 2014 at 09:39

Sigh, another badly worded wiki page.

The intent of the highway= tag has always been that the tags represent each road's importance in its nation's road system, with the hierarchy trunk->primary->secondary->tertiary->unclassified.

There are also a few "special" values: highway=motorway (a restricted access fast road), highway=residential (a sub-unclassified road for residential access), highway=service (a sub-unclassified road for non-residential access), and so on. But the trunk->unclassified hierarchy covers most of it.

This is 100% applicable to any other country, and indeed the wiki page says this - "The highway type helps indicate the importance of the highway within the road network as a whole" - but, in the way of wiki pages, has accumulated a bunch of cruft which serves mostly to confuse people. We just need to sort the cruft out, rather than implementing a whole "new set of standards", I think.

Comment from SK53 on 10 January 2014 at 15:49

Just a minor note:

highway=primary in the UK can refer to:

  • a divided road with some junctions not at grade, 4 lanes
  • a undivided road with 4 lanes
  • a road with 2 lanes
  • a road with 1 narrow (<5 metre) lane with passing places

So, even in the UK we have always had the notion that OSM highway tagging is a Functional classification. It so happens that the original highway classification in Great Britain was functional too.

We also have plenty of unpaved residential roads (and many are located in the SE: the 'By roads “not adopted”' of John Betjeman.

Unfortunately as Richard points out there is a tendency to reverse engineer wiki definitions from a subset of OSM data (i.e., usually prevailing practice with a few km of author's home patch).

Comment from z-dude on 11 January 2014 at 06:01

My experience has been that people are trying to force their personal standards over other people. I don't recognize the Proposed Africa page as valid due to the current lack of participants in it's discussion, and I don't think a handful of people on that page have the authority to tell OSM how to map the roads of a billion people in Africa.

When you go and delete someone's ways because they drew a track instead of a primary road, then there's something wrong with your people skills.

Login to leave a comment