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I'm trying to perform an OD Cost Matrix calculation on a set of points using a road network from OpenStreetMap data. The network contains lots of roads that don't connect to the rest of the network. In the case where a point snaps to such a place on the network, it can't reach any other sample points.

How do I remove these sections of road? Or if that's not possible, how could I systematically identify those areas and connect them to the rest of the network?

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  • Would you be able to edit your Question to include a picture of what your data looks like? Also, what version of ArcGIS for Desktop are you using, and is your data stored in a file geodatabase or something else?
    – PolyGeo ♦
    Apr 7, 2014 at 1:52
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    Disconnected line segments are difficult to spot in the vector model ArcGis uses; when ESRI was using coverages they were easy to find (DrawEnvironment Node Dangle). I have found disconnected end points using feature vertices to points with both end option and then event rendering to compile end counts. The unattached ends have a count of 1 I exported then joined to the lines - any that had both ends with a count of 1 are isolated. This will only work if the lines are planar (i.e. end-on-end).
    – Michael Stimson
    Apr 7, 2014 at 3:19

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My solution to this was kind of a kludge, but then I was doing a small class project working with a subset of one county's roads so the network wasn't that big and I didn't need to do it as a common task. I just ran a service area analysis with the time set large enough that in theory everything should be reachable. That highlighted everything that was connected, thereby showing what wasn't. Some of them I added new connections because I needed to preserve those areas, others I simply selected and deleted the isolated roads from the dataset.

10.1 help has reference to a Find Disconnected tool on the Utility Network Analyst Toolbar if you have access to that.

10.2.1 also has a new tool that might do what you want, if you have access to that version or higher: Find Disconnected Features In Geometric Network (Data Management)

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  • Large enough time for service area solved my problem! thanks! +1
    – Red
    Jun 17, 2017 at 20:26
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I was looking for a possibility to delete isolated lines from OSM data, too. Unfortunately, I have a huge amount of data. And having to deal with Network Datasets anyway, I just didnt want to examine Geometric Networks. But using Michaels suggestion worked, thank you very much! I had to change 2 things: First, I had to unsplit the lines in the beginning, so that I was been able to delete also isolated parts that consists of more than 1 feature line. Second, the last step consists of a query to the lines with a joinCount of 2 (istead of a iCount of 1). My data is preprocessed OSM data, stored in a file geodatabase. Here are the detailed steps:

  1. Make a copy of the roads dataset -> roads_copy
  2. Use "unsplit line" tool on roads_copy -> roads_unsplit
  3. Use "feature vertices to points" tool on roads_unsplit (point type: both ends) -> roads_vert
  4. Use "collect events with rendering" tool on roads_vert (quite time intensive) -> roads_collect (unattached ends get ICOUNT = 1)
  5. Query roads_collect: "Select from roads_collect where ICOUNT = 1"
  6. Export query result -> roads_icount1
  7. Use "spatial join" tool to join roads_icount1 (= join features) to roads_unsplit (= target features); choose "one_to_one", "keep all target features" and "intersect" -> roads_join (isolated roads get Join_Count = 2)
  8. Query roads_join: "Select from roads_join where Join_Count = 2"
  9. Use "select layer by location" on original (not unsplitted!) roads; selecting features = roads_join, relationship = "share_a_line_segment_with", selection type = "new_selection"
  10. Delete selected rows using "delete rows" tool

There you go. Maybe put it in a model. It seems a little complicated but leads to the desired result for me.

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  • I followed AriJane's method and it worked, however, some false positives will be returned if line 'a' connects to the vertex of line 'b' (such as a T-intersection) and that vertex on line 'b' is not an end point. If the 'false positive' line is a bridge/overpass/underpass, all of the lines that intersect will also be deleted. For a dataset with ~185,000 line features @ step 2 above, the whole process (steps 2-10) took 14 minutes. The tool mentioned by Chris W, found here is only available @ 10.2.1 and above.
    – L Tyrone
    May 21, 2015 at 6:35

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