[OSM-talk] Map Features: Road classification schemes for worldwide use

[Wollschaf]

On Fri, 01 Sep 2006 09:13:06 +0100, Etienne wrote:

> Does C=t or is t>C?

I assumed that t > C.

> Agreed this should be country specific.  To be more precise it is
> administration specific.  New South Wales has a different set of road
> classifications to Western Australia, for example.  In most cases there is
> one scheme per country but there may be regional administrations that have
> different rules.

Argh. So we'd have to add a country and region tag; wayclass=au:nsw:1 is
another option.

> In the UK the terms motorway, primary, secondary are well defined and
> fairly well understood.  I don't see the need to code this using numbers,
> especially as this would cause problems the moment some administration
> decides to introduce some intermediate classification.  uk:primary,
> uk:motorway etc would work for me.

Of course they work for you. But for many other countries, they don't. So
we have to find a solution soon ;)

Translating local classification names to english causes problems, and
users will have to look up the equivalent names. There will be
interpretation and guessing involved. Having to look up each road class is
the only problem with a numbered scheme, too; So why not use that one?

Simply not translating local classification names makes it impossible for
ASCII-speaking users to edit roads in - for example - japan or russia. I
would like to be able to create maps should I ever get there.

Changes in the classification scheme are a problem for a numbered scheme.
This could be adressed by reserving 1-9 for motorways and dual-carriage
roads, 10-19 for primary and generally the most important roads, 20-29 for
secondary and so on (70-79 residential?) It makes tagging a bit more
complicated as you'd need a reference sheet; having numbers only count up
from 1 to n makes it pretty easy to deduce the correct number.

A numbering scheme with defined equivalents is very easy to render, as
dual-carriage roads are defined by anything <10, while everything else
gets smaller and a different color every time a decade is crossed. The
exact equivalents only have to be known to humans, and software does not
really need to know that 5x defines a minor road; It's just rendered
smaller. Exact equivalents are just needed for the map legend.

happy mapping,
Wollschaf