[OSM-talk] Highway=trunk : harmonization between countries ?
colin.smale at xs4all.nl
Tue Aug 22 11:29:10 UTC 2017
The road classification suggests a default maxspeed, in the absence of
more explicit information. I don't understand why junction penalties
should be dependent on the road classes, and not on physical
characteristics. I guess this is just a heuristic which can be useful if
you don't have the full picture.
I would like to take a closer look at your example route... Can you give
start and end locations?
On 2017-08-22 13:13, Lester Caine wrote:
> On 22/08/17 11:41, Colin Smale wrote:
>> I agree, classification should be largely irrelevant to routing.
>> Routing needs timings from node to node, which are best derived from
>> bendiness, number of lanes, junctions etc and then capped to the legal
>> maximum. A four-lane secondary, primary, trunk or motorway will all have
>> the same effective speed in the absence of bends and junctions.
> The problem here is that most routing systems use the highway= tag as
> the initial key to defining the 'defaults' for a link and the delay
> elements added moving from one type of road to another. I am convinced
> there is a problem with the tagging of the B4632 which is preventing it
> from being seen as an alternative to the A46 10 mile detour but as yet
> I've not spotted anything wrong. Shortest routing will pick it up, but
> then avoids the M40/M6 for the next stage :( It's not just OSM routing
> that gives problems, other routing engines are showing similar detours
> around local 'shortcuts' ... so even within a single country
> harmonization is a problem ...
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