OpenStreetMap
Proper tagging for conditional restriction and which services are reading them?
Posted by jimkats on 21 December 2020 in English.Context on why this post-question:
Two days ago there was an incident in my area where a truck went through the city center even though it shouldn’t, and damaged a street sign while trying to turn. According to the article of a local blog, the truck driver said he was confused by the GPS and went the wrong way. No mention on which GPS he was using, but regardless that made me wondering of how I would tag to make such trucks go the proper way.
At the point where the driver took the wrong turn, there’s a visible traffic sign (the one shown below). Personally, that raises the question on why he followed his GPS routing instead of the traffic sign, assuming he saw it beforehand, but that’s not the point of this post anyway.
(photo is mine)
The traffic sign, which is not listed in the Greek Highway Code, means that if the heavy truck is above 10 tons, then turn left.
After asking other Greek mappers, the answer I got (and as I just implemented) as for what could work is:
For the traffic sign itself:
* traffic_sign=maxweightrating
* maxweightrating:hgv=10
* restriction:hgv:conditional=only_left_turn@(maxweightrating>10)
And then for the other road of which the traffic sign mentions, in this case the right road:
* maxweightrating:hgv=10
My other question is, do we know which routing services/apps use such data? That is, those specific tags for conditional restriction.
I know that we can’t know for sure how many routing services use OSM data and from those, what kind of data they are parsing.
Discussion
Comment from SimonPoole on 21 December 2020 at 12:35
osmand supposedly supports conditional access for some combinations.
But nothing is likely to support what you tagged: - maxweightrating is essentially unused compared to maxweight - conditional restriction tagging in turn restrictions isn’t supported by anybody afaik (and the comment wrt maxweightrating applies even more here) - in general the conditional tagging grammar is massively underspecified and mainly serves to humour people that think stringing long combinations of tags together is a good idea and will actually do something.
The question is, why tag it in such a complicated and likely non-functional fashion in the first place? Simply add maxweight:hgv=10 to the road segment going straight on (and if necessary any thing going off to the right) and that should force router that support maxweight:hgv to not plan the route straight on and plan a turn to the left (if you feel better about it you can add maxweightrating:hgv tags too).
Comment from jimkats on 21 December 2020 at 23:36
Thanks for the response
Since the definition of the sign isn’t quite clear if it’s about defined or actual weight of the truck, it indeed makes sense to add the maxweight key, even additionally with the other key, just to be “clear” in case any app will actually use it.
Comment from kucai on 23 December 2020 at 02:38
Is the hgv tag necessary? Isn’t maxweight already absolute? Just wondering.
On another note, I believe that truckers of big companies usually have their own commercial gps apps that is already complete with weight and height (and even time of day) restrictions built in.
Comment from jimkats on 23 December 2020 at 03:54
I guess it’s necessary because most signs show weight of trucks and not just any vehicle (assuming the local traffic code has a generic vehicle sign for max weight). So, why not tag it for hgv if the sign explicitly refers to trucks and not just any type of vehicle? Regardless of practicality.