[OSM-talk] definition of the main highway-tag

[Christiaan Welvaart]

On Fri, 31 Jul 2009, Martin Koppenhoefer wrote:

> If the administrative class in your country coincides with the
> importance: fine. Nothing changes. Unfortunately this is neither in
> Italy nor in Germany the case: some roads have been downgraded /
> passed to a lower maintenance entity for administrative reasons (now
> somebody else pays and cares for the maintenance, what was before a
> nation / federal road has sometimes become a regional / Landstraße).
> Others, like Kreisstraßen in Germany (comunal roads) have been
> upgraded and are now almost Autobahn-Standard.
>
> As result of this, it has been agreed not to corelate administrative
> status and highway-class. But there is a problem with tagging pure
> physical state as well: it depends on the context. In a rural area a
> secondary or primary street will be much smaller than in a highly
> dense urban area. This is why importance of the road seems most useful
> (be it for routers or to structure visually and according to
> significance on rendered maps).

Why would who maintains a road directly determine its administrative 
classification? If a municipality decides that some road is a motorway, we 
better tag it as such. In The Netherlands some provinces maintain short 
stretches of motorway, for example, while most motorways are maintained by 
the national government. The maintainer of a road can be tagged 
independently. So is it really a big change for Germany and Italy to 
define the highway tag as the administrative classification of the road?

The problem with 'importance' is that it is too vague and it is the task 
of the road maintainer to determine/define a road's function. Also, if 
there is a mismatch between a road's classification and its 'importance', 
we should tag the classification. The importance is derived from the 
topology of the road network, which is already in OSM. An example is a 
route through a town to a motorway access. The municipality this town 
belongs to considers this route inappropriate, while the municipality 
where the route starts considers it an appropriate route. The road inside 
the town is still tagged as secondary, while its maxspeed was already 
lowered to 30km/h. AFAIK its 'importance' has not changed, however, as no 
alternative route to this motorway access is available (there are several 
alternative access points to this an other motorways, though). So, do you 
think we should keep it as secondary which probably matches its importance 
(access to a motorway) or tag it as tertiary or even lower which matches 
its classification (only meant for traffic from and to the town)?


     Christiaan