[OSM-talk] Speed tagging
jon at siliconcircus.com
Sat Aug 4 10:48:01 BST 2007
Alex Mauer wrote:
>> Way 1, W->X maxspeed=50
>> Way 2, X->Y maxspeed:hgv:a=30;maxspeed:a=50;maxspeed:b=50
>> Way 3, Y->Z maxspeed:a=30;maxspeed:b=50
> I would use "left" and right" instead of a/b, or "opposite" instead of b.
I'm going with
Way 1, W->X maxspeed=50
Way 2, X->Y hgv:maxspeed:opposite=30;maxspeed=50
Way 3, Y->Z maxspeed:opposite=30;maxspeed=50
(The segments/ways are pointing uphill, the ways in my mail are the
"wrong" way round)
Since we already have a hgv tag elsewhere, I'll leave that hairball for
someone else and use it.
I picked "opposite" over "left"/"right" because "opposite" only needs a
route planner to know in what direction it wants to travel over the
segment. "left"/"right" needs the planner to know its direction over
the segment *and* to know that you drive on the left/right-hand side of
the road at this lon+lat...
I'd imagine a route planner doing something like:
- If travelling in the direction opposite to the segment direction,
search for "<vehicle class>:maxspeed:opposite"
- If travelling in the direction opposite to the segment direction and
the above tag wasn't present, search for "maxspeed:opposite"
- If travelling in the segment direction, or if the above tags weren't
present, search for "<vehicle class>:maxspeed"
- If no tags yet found, search for "maxspeed"
- If still nothing found, take some sensible default based on the
highway class. ("sensible" depends on national boundaries, but this is
the route planner's problem, not ours)
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