[Tagging] How to tag: Legally separated ways

Alberto albertoferraris at fastwebnet.it
Tue Oct 16 00:21:45 GMT 2012


Please read carefully:
one thing is a legal barrier (e.g. continuous line), one thing is a real
barrier (e.g. guard rail, Jersey barrier).
A legal barrier can be crossed by a vehicle if necessary, a real barrier
not.
We don't need to tag any exception for emergency vehicles. The routing
software (now or in future) can be set to ignore legal barriers in emergency
navigation.
But if we don't tag in different ways legal and real barriers, there is no
way to distinguish them.
Think to this case: a motorway with continuous line and another with
guardrail in the middle, and your destination is behind you. If routing
software can't distinguish them, it will in both cases suggest to take the
first exit 5 km ahead, and it may calculate a tortuous route along secondary
ways.
In your GPS you see "5 km ahead, go right" and a part of the route. If you
don't know that your destination is just behind you, how can you imagine
that the suggested route is misleading and you can simply do a U turn?
In emergency situations you have many things to pay attention to and maybe
you don't notice that GPS is wrong. I know these situations, I'm a fireman.
Ok, usually you know your operating zone and you can ignore GPS, but why
should we deliberately put incorrect data in the map?

By the way, in all cases of motorway junctions probably option b) is fine
too, there is no much difference.
But it is important to understand that using option b) for longer ways
implies turning a legal barrier into a physical barrier, and that can
produce unwanted and unexpected consequences.

>Having said that there are certain restrictions which they would do well 
>to follow, such as maxheight and maxwidth. If it don't fit, it don't 
>fit, with or without blue lights!
Exactly, and a guard rail is one of those restrictions that you can't pass
with or without blue lights, we should distinguish it from a line drawn on
asphalt.

> why should we compromise "service" to the vast majority of real users for
the hypothetical benefit of the very few.
I can't see how the service can be "compromised". We can anyway refine and
use divider proposal:
http://wiki.openstreetmap.org/wiki/Proposed_features/Divider

Cheers
Alberto




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