[Tagging] Tags useful for rendering of roads in poor conditions

Fernando Trebien fernando.trebien at gmail.com
Tue Dec 31 16:10:33 UTC 2013

Hello everyone,

I've been interested in proposing a change to Carto's style (Mapnik's main
style) to allow visual identification of unpaved roads for any kind of
road, much like the Humanitarian style does, which bases this decision on
values of the surface tag. The Brazilian community has shown interest on
this many times, since lack of this feature causes unaware users to
classify roads incorrectly. David Bannon proposes (below) that we use the
tracktype tag for that instead, but I've never seen it being used for
anything besides roads with highway=track (therefore, not a very common
practice it seems). Do you think we should encourage its use in conjunction
with unclassified, tertiary, secondary and primary highways?

It seems to me that surface=compacted is quite similar in meaning to
tracktype=grade1 (whereas surface=sand, surface=dirt, and others, could be
equated with other grades but rarely with grade1, particularly because the
"compacted" value exists) and so both tags could be used for the same
rendering purpose. Do you agree?

I've seen people from different countries requesting different things on
this topic: some would consider even a sett street "unpaved" (therefore,
requiring special rendering), but it seems that a "compacted unpaved" road
is the limit with which few would disagree. Finding the right universal
threshold (if there is only one) is still pretty much debatable, so
opinions are appreciated.

---------- Forwarded message ----------
From: davidbannon <notifications at github.com>
Date: Tue, Dec 31, 2013 at 4:02 AM
Subject: Re: [openstreetmap-carto] Render paved/unpaved (#110)
To: gravitystorm/openstreetmap-carto <openstreetmap-carto at noreply.github.com
Cc: ftrebien <fernando.trebien at gmail.com>

I am not sure the tag surface= is the right one here. It has a lot of
possible values, and a lot of them in use. We'd need a look up table to
decide what to do. Better, in my humble opinion to use the tracktype= tag.
This tag is intended to show what state the road is likely to be in and
thats the information a user really needs. Further, this tag is very widely

The Australian Tagging Guidelines on OSM discusses this (
and believes that any road with tracktype= asserted needs to be shown
people are aware its not a sealed road.

Please remember that highway= type tags should show what a road is is
intended for, further information is needed if the surface of that road is
not what might be expected ! This is particularly important in places like
the Australian Outback where long distances are involved. Many people have
died as a result of them underestimating their ability to use a particular
road. I don't want to see OSM mentioned in a coroners report.


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Fernando Trebien
+55 (51) 9962-5409

"The speed of computer chips doubles every 18 months." (Moore's law)
"The speed of software halves every 18 months." (Gates' law)
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