A recent discussion on the [osm-dev list] (http://gis.19327.n5.nabble.com/Renderer-issue-highway-service-and-service-driveway-tt5791858.html) 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
- 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.
- 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
- 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.
- The existing Highway page should moved To a Highway_Tag_United_Kingdom and modified accordingly
- The numerous pages associated with road standards should be combined/cross-linked
- The International Equivalence should be translated to English, and mappers encouraged to provide full translations of the page
- A standardized country specific highway template should be designed.
- 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.