[OSM-talk] OpenStreetMap routing service

[Dermot McNally]

2008/9/7 Lambertus <osm at na1400.info>:
> I think it's fair to assume that a cyclist isn't allowed on that type of
> road on mainland Europe anywhere...Anyway, global routing using only a
> single definition for max (average actually) speeds and other properties
>  for roads isn't optimal.

I agree with the second half of what you say here, and that's because
I disagree with the first bit. I know that German tagging practice has
evolved to consider "trunk" to refer to vehicle-only routes, but
there's no reason to suppose that other countries will use the same
reasoning. The term originates in the UK road classification system,
where it's simply the highest category of non-motorway road. Within
that category, quality can vary greatly between motorway-standard
roads and glorified cart tracks.

This same situation applies next door in Ireland. Other countries are
as likely to be like UK and Ireland as they are to follow German
practice. Basically, it just shows that we can't trust the highway
classification to give us any hints other than the following:

Vehicles only and high speed: motorway only
max practical speed: where maxspeed is provided
suitability for vehicles, bikes and pedestrians: where access is provided
Interruptions to traffic flow, with the capacity to limit speed: where
traffic signals, roundabouts, mini-roundabouts, crossings or
non-*-link roads join a road.

Other inferences on road class, if you wished to draw them, would need
to change from country to country, and that doesn't seem scalable.

Dermot

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