[Tagging] Lane geometry in OSM

John Lambert johnwlambert at gmail.com
Thu Aug 2 18:57:29 UTC 2018

Hello OSM Tagging,

I have a question about the use of detailed lane geometry to OpenStreetMap,
like (1) lane centerlines, or (2) lane boundaries, (3) variable lane width,
or (4) lane connectivity.

Currently, all I see are:

*(1) how many marked lanes are there on a highway, e.g. <tag k="lanes"

*(2) which lanes on a two way road are not distributed evenly between the
driving directions <tag k="lanes:forward" v="3"/>, <tag k="lanes:backward"

*(3) the "turn=*" key, specifying the indicated direction in which a way or
a lane will lead for turning or merging, e.g. <tag k="turn:lanes"
v="reverse|through|through;right|right"/> <tag k="turn:lanes"

*(4) uniform lane width*
*width:lanes, width:lanes:forward, width:lanes:backward, maxwidth:lanes,

It seems like we would need a "Way" to describe each lane's centerline. My
understanding is that it is not permitted in OSM to add an extra "Way" tag
to a specific lane tag currently. Is this correct?  I have heard from
another user that the lane centerline model was the previous OSM model, but
was scrapped and replaced with the current road centerline model.

Also, another question I have -- would a line width have to be uniform
across an entire "Way," or can different line widths be expressed for each
separate chunk of the Way?

I saw that there is a key that a few people have used: width:lanes:end
<https://taginfo.openstreetmap.org/search?q=width%3Alanes> and
<https://taginfo.openstreetmap.org/keys/width%3Alanes%3Aend>. I did not see
these in the OSM documentation. Are these just fields that people decided
to add without approval? Shouldn't the OSM server reject such an upload?

I saw that a proposed feature is street area
<https://wiki.openstreetmap.org/wiki/Proposed_features/Street_area> (or
similarly area:highway), where a Way would depict the polygon area of a
street, but I'm interested in even more informative lane geometry than
this. My understanding, is that this proposed feature will only allow the
enumeration of drivable road areas, and not per-lane width/boundaries.
There is a figure shown here

Thank you in advance for your time.

Best wishes,
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