When measuring the width of a way, do you measure from gutter to gutter, or shoulder-line to shoulder-line, for example; or, do you exclude the area taken up by habitual on-street parking?

asked 09 Apr '16, 11:34

samuelrussell's gravatar image

samuelrussell
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I would measure the with from kerb to kerb or end of the paved area if there is no kerb.

street with overlaid measurement arrows
(own illustration based on a photo by Thisisbossi, license: CC BY-SA 3.0)

That there is street parking possible can be indicated by a tag with the key parking:lane. That there is a shoulder can be indicated by a tag with the key shoulder. All those are part of a street, are they not? … and users of the data could take those extra tags into account (e.g. when calculating if a over-width vehicle can use this street).

Definitely I would include the parking space if it is subtracted from what is a driving lane if no one parks there ... I am not that sure about the shoulder. If there is a shoulder tag on the highway way I would assume that the width includes the shoulder, as it is mapped as the same object which carries the width. A bit questionable what to think if there is no shoulder tag. And I think, we have no definition of what to include in the width of a "highway".

Some further thoughts: Okay, so, what if a way with a highway tag and a width tag also has a sidewalk tag? Since the width tag is tagged on the way it applies to the whole way – so, if the way includes a sidewalk=both then width needs to include the sidewalk. Mindblowing... More specific width tags may make more sense, I guess. width:carriageway (184 uses) maybe?

We have currently 2037 width:lanes tags, which likely specify the width of the single lanes (see the values at taginfo, too). Maybe specifying this makes more sense – depending on your use case.

Or tag the width of the shoulder in addition to the overall width: width:shoulder (881 uses) or shoulder:width (1906 uses).

I assume, that in the beginning of OSM, when there were no sidewalks, parking lanes, shoulders and stuff tagged onto the same object on which the highway tag was on, the width just meant the width of the carriageway (possibly including such facultative parking like in the photo). While writing this answer I more or less came to the conclusion that, nowadays, a unspecified width tag does not make much sense for ways which have a highway tag, because it is not clear what is meant by it.

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answered 09 Apr '16, 21:30

aseerel4c26's gravatar image

aseerel4c26 ♦
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edited 10 Apr '16, 11:29

Thanks for width:carriageway in particular.

(10 Apr '16, 07:28) samuelrussell
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You need to be a little careful with some of these taginfo numbers - in some cases they've been created either mechanically or by humans, but without brain being in gear. For example, I randomly picked a "shoulder:width" and got to http://www.openstreetmap.org/way/391523093 . Obviously (both logically and from the imagery) there's no shoulder at all here - clearly the way for the main carriageway has been split and the extra tags simply haven't been noticed.

(10 Apr '16, 10:23) SomeoneElse ♦

@SomeoneElse: thanks for the note, indeed, I quoted those numbers just for ease of reading (no need to click through to taginfo each time if you want to know the number). High numbers do not necessarily mean that a tag is used by many mappers or is useful and well-thought-out at all.

(10 Apr '16, 11:10) aseerel4c26 ♦

I read the following:

  • width = undefined, OR, a, OR c, OR f, OR m+n
  • roadreserve:width = a
  • sidewalk:width = b or j, thus :left & :right
  • width:road = f
  • width:carriageway = m+n
  • width:lane:forward = m
  • width:lane:backward = n
  • parking:lane:left:width = g
  • parking:lane:right:perpendicular:off-road:length = d
  • shoulder:width:left = g
  • shoulder:width:right = d or h, depending on the way
  • traffic_calming:island:width = k
  • cycleway:backward:lane:width = i
  • width:verge = e

LPI NSW Base Map, Birriga Road NSW LPI NSW Imagery, Birriga Road NSW

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answered 10 Apr '16, 07:54

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samuelrussell
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edited 10 Apr '16, 11:07

aseerel4c26's gravatar image

aseerel4c26 ♦
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Whilst you can of course use any tags you like, a quick look at the usage of https://taginfo.openstreetmap.org/keys/parking%3Alane%3Aleft%3Awidth shows that only 3 mappers worldwide are using it. It's likely that the only maps using that data will be ones that they create.

"roadreserve:width" isn't used at all; you'd need to both explain what it meant and persuade other people that it's useful with that one.

(10 Apr '16, 10:27) SomeoneElse ♦

I'm more pointing out the variety of objects that a width on a way might point to. The wiki isn't particularly good source to inform tagging style here. Neither, for that matter, is the :lanes suffix style.

(10 Apr '16, 21:58) samuelrussell
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question asked: 09 Apr '16, 11:34

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last updated: 10 Apr '16, 21:58

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