[OSM-talk] Speed tagging

Jon Bright jon at siliconcircus.com
Fri Aug 3 23:30:27 BST 2007


Map_Features specifies "maxspeed" as speed in km/h.  I have a number of 
questions about this:

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?

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?)

3. How should differing speed limits for differing classes of vehicle be 

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.

I'm guessing "HGV" is a UK legal definition ("Heavy Goods Vehicle"). 
"Lorry" is the British English.  "Truck" would be the US English(?). 
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.

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

Does anyone have better suggestions? Or a way ID where someone already 
mapped such a thing?


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