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The book OpenStreetMap: Using and Enhancing the Free Map of the World by Ramm, Topf, and Chilton (urn:isbn:978-1-906860-11-0) suggests using relations with type=dual_carriageway to help express that parallel ways form part of a divided dual carriageway. Are there any consumers of this data, either for rendering or routing, anywhere in the world? (And, relatedly, does it matter? If we build it, might they not come?)

There are currently 997 uses of this tag for relations in the OSM database, but no machine-accessible documentation, so I might upgrade the proposal for it to something documented as a de facto tag.

asked 05 Jun '11, 14:15

Andrew%20Chadwick's gravatar image

Andrew Chadwick
accept rate: 25%

edited 05 Jun '11, 17:34

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Richard ♦

In mind is that in the UK, roads (excluding motorways) specifically marked as a dual carriageway would be subject to a national speed limit of 70 mph for cars, and 50 mph for HGVs; compared with 60 and 40 on single carriageways. These would be usually signified with a 'dual carriageway' sign at the commencement, and the upside down Y sign at the end (as opposed to the two way traffic sign, which may be used additionally to provide a further warning.

Short separated ways at say, intersections, as far as my understanding of traffic laws goes at least; would not be a type of dual carriageway, and would therefore have the lower limits - therefore the tag should probably be documented properly.

Cheers Chris

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answered 05 Jun '11, 23:35

c2r's gravatar image

accept rate: 18%

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question asked: 05 Jun '11, 14:15

question was seen: 6,254 times

last updated: 05 Jun '11, 23:35

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum