Why are streets often split into several ways on OSM?

examples:

  • "campus drive, stanford"
  • "kirchengasse, vienna"
  • "the bowery, nyc"

asked 05 May '14, 20:13

snupo's gravatar image

snupo
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accept rate: 0%

edited 06 May '14, 01:15

aseerel4c26's gravatar image

aseerel4c26 ♦
32.3k16241553


Streets are split when one or more properties are different along the street. A non-exhaustive list of such properties would include:

  • Speed Limits
  • Number of Lanes
  • Parking restrictions
  • Nature of street lighting
  • Bus routes along the street
  • One way sections
  • No left/right turn restrictions which require a via point
  • Changes of jurisdiction (where say, house numbering restarts)
  • Change of surface: asphalt to concrete, asphalt to dirt, etc.
  • Nature of the source data (some part may have been seen by a mapper, the rest completed from imagery)
  • Presence or absence of sidewalks
  • etc

Streets are naturally represented as several ways if they are not linear, or if they are dual carriageways.

If a street is split it is best NOT to recombine sections unless using JOSM which forces a check on all mismatched tags. Creating multilinestring topologies representing all parts of a named street should be done outside OSM as a processing step on an extract. For most streets this is trivial, but there are a number of well-understood exceptions which can create problems and for which there are no good widely available solutions.

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answered 05 May '14, 21:46

SK53's gravatar image

SK53 ♦
24.0k46240378
accept rate: 21%

Ways are split when the attributes/tags change (and when relation membership changes too).

A random example: the speed limit changes, you slplt the way and apply the new speed limit.

This does lead to sometimes very small segements (joke for old hands), but is perfectly OK.

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answered 05 May '14, 21:44

SimonPoole's gravatar image

SimonPoole ♦
41.0k13300649
accept rate: 19%

edited 05 May '14, 21:45

-2

Are they Dual-Carrage ways; with a barrier between the two one way parts? They can be split to help routeing especially when only one half of the road links to a paticular side road.

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answered 05 May '14, 20:30

Govanus's gravatar image

Govanus
1553711
accept rate: 3%

How does splitting a road help the router?

(06 May '14, 07:31) scai ♦
4

I think they're referring to the separately-mapped oneway parts as opposed to a single way representing the entire dual-carriageway, but that has nothing to do with the original question.

(06 May '14, 18:39) alester

the router can more easily handle when traffic can't cross between the carrageways at junctions

(01 Mar '16, 19:11) Govanus
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question asked: 05 May '14, 20:13

question was seen: 2,885 times

last updated: 01 Mar '16, 19:11

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