[OSM-talk] Speed tagging

Alex Mauer hawke at hawkesnest.net
Sat Aug 4 00:03:19 BST 2007


Jon Bright wrote:
> 1. I've just been entering numbers here ("60"), but I've seen some 
> entries that are including units ("60km/h").  Is there any general 
> consensus on which of these is right?

If the speed is specified to be in kph, then units should not be used.

However, this does lead to awkwardness when conversion gives the
appearance of excessive precision (US: 65mph -> SI:104.60736kph).  For
this reason it may be better to include a unit.

> 2. How should differing speed limits in opposing directions on a two-way 
> road be represented?  I'm thinking something like maxspeed:a=50, 
> maxspeed:b=30 would be needed, where "a" represents the direction of the 
> way and "b" the opposite direction?  (I saw a question recently about 
> the same thing with differing street names, which used "left" and 
> "right", which may be better?)

Perhaps "maxspeed" and "maxspeed:opposite"?  (or maxspeed:left and
maxspeed:right would be good as well)

> 
> 3. How should differing speed limits for differing classes of vehicle be 
> represented?
> 
> I've today mapped the limits on a road.  One stretch causes me 
> particular trouble.  It's a steep downhill towards a sharp curve.  In 
> the uphill direction, the limit is 50 for all vehicles.  In the downhill 
> direction, it's 50 to start with, dropping to 30 for lorries/HGVs, then 
> dropping to 30 generally about 200m later.

maxspeed=50; hgv:maxspeed=30 is how I would tag that downhill section.

> 
> I'm guessing "HGV" is a UK legal definition ("Heavy Goods Vehicle"). 
> "Lorry" is the British English.  

Doesn't "lorry" cover stepvans, (http://www.walkinvan.com/ ) and "Luton
body" vehicles (http://en.wikipedia.org/wiki/Luton_body ) which are
often used as moving vans (http://www.uhaul.com/trucks/ ) as well?  I
assume the latter would fall under "goods" otherwise...I'm very unclear
where that line is.

> "Truck" would be the US English(?).

"Semi" or perhaps "rig" would be the US English. Less common are
"tractor-trailer" as well as the complete but awkward term
"tractor/semi-trailer rig"

> The road's in Germany and I guess "LKW" or "Lastkraftwagen" would 
> therefore be right for Germany.  It's (probably) a universal concept, 
> both in itself and in terms of frequently having special restrictions on 
> roads, but no universal term occurs to me.

Same here.  I think the initialisms are very bad for international
comprehension though (be it HGV or LKW).  I expect "Semi" is equally
bad; right?

> Assuming the node at the top of the hill is W, the node where the 30 
> restriction for HGVs starts is X, the node where the general 30 
> restriction starts is Y and the node at the bottom of the hill is Z, my 
> best guess on how to represent this is:
> 
> 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.

-Alex Mauer "hawke"

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