[Tagging] uphill vs. incline=up - direction of travel

[Patrick Strasser-Mikhail]

Hello!

I have need for tagging that a restriction on a road is only valid in 
case a vehicle is driving uphill.

The traffic sign states "Snow chains required when ice or snow on road, 
except for AWD cars driving uphill"[1]. This is indicated on both sides 
of the road section, both driving uphill and downhill.

That would call for a conditional [2] specification of a direction or 
condition with the aspect of direction in relation to elevation.

The first idea was to use 'incline=up' like in
   snow_chains=required @ (ice; snow)
   snow_chains:motorcar:conditional=default @ (awd AND incline=up)

It was pointed out[3] that 'incline' is a tag and intended to indicate a 
*direction* and amount of inclination of *the road in relation to the 
mapping direction*, not the direction of the *vehicle driving* on the road.
**'uphill'** was proposed.

There is however a accepted specification for relative direction 
longitudial-wise in relation to the way: Forward, backward, left, right 
[4][5][note 1].
These are defined to be used as key suffix or value.

The improvement seems to be to instead use 'uphill' either
as direction as key suffix
   snow_chains=required @ (ice; snow)
   snow_chains:motorcar:uphill:conditional=default @ awd

or as condition
   snow_chains=required @ (ice; snow)
   snow_chains:motorcar:conditional=default @ (awd AND uphill)

The direction key suffix approach seems to integrate better, but mappers 
could mistake it and use it instead of :forward and :backward, making it 
impossible to interpret without inlination information. Using it in the 
condition seems to split direction information from other direction 
information.

What do you think?

Best Regards

Patrick/trapicki


[1] 
https://wiki.openstreetmap.org/w/index.php?title=Proposed_features/Snow_chains&oldid=2451441#Examples
[2] https://wiki.openstreetmap.org/wiki/Conditional_restrictions
[3] 
https://wiki.openstreetmap.org/wiki/Talk:Proposed_features/Snow_chains#uphill_vs._incline
[4] https://wiki.openstreetmap.org/wiki/Forward_%26_backward,_left_%26_right
[5] https://wiki.openstreetmap.org/wiki/Proposed_features/right_left

[note 1] I could not find an accepted proposal for that, bit was 
implicated in the the proposal for conditional restrictions that it was 
accepted at that time of the :left and :right proposal in 2009 
https://wiki.openstreetmap.org/w/index.php?oldid=813491#What_about_:forward_and_:backward?
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