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I want to get the shortest paths from some points to the nearest highway junctions. I extracted the highway junctions by doing the Intersect function from the network junctions and selected highways. Then I created the network database and did the Closest Facility Analysis (highway junctions for facility and points for incidents) to get the shortest path from the points to their nearest highway junctions. The problem is some of the obtained "shortest paths" are not the actual shortest paths since they skip the nearest highway junctions. It seems the highway junctions extracted from the network are not perfectly aligned on the network. I tried to use Integrate to integrate the highway junctions and network, and then recreated the network database, but it still didn't solve the issue. The following pictures show the problem. The red line represents the highway. The purple dots represent the highway junctions. The purple square represents the point needed to be analyzed to get shortest path.

Any suggestions?

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I am using the ArcGIS Desktop 10.3.1 Advanced License.

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It seems the highway junctions extracted from the network are not perfectly aligned on the network

This sounds the most likely cause of the problem. Since you have an Advanced license, you can create a topology and set rules to ensure that the highway junctions align perfectly with the roads.

You can use the topology to snap the junctions to the roads, and ensure that the roads have a vertex where the junction is located.

Then once you have ensured good connectivity you can delete the topology and recreate the geometric network (a geodatabase can't have both of these at the same time)

  • Thanks for your information. I followed your method that first I create a typology having highway junctions and network. I use the rule Point Must Be Covered By Line to validate the typology, but I didn't get any error in the end. Did I use the right rule? Or if there has anything I have to pay attention. – Tianxin Li Aug 30 '16 at 14:44
  • Can you offer more details of your method? I can check if your method works for my case or not. Given your current information, I didn't find any errors in the Topology. – Tianxin Li Aug 31 '16 at 3:42
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I think I got the answer for my question. I tried to use the method from Stephen but failed. I have to find another way. The method I used is to join the highway junctions to the network junctions. In this way, I can identify the highway junctions on the network junctions layer and don't need to extract the junctions to create another layer. In this way, I get rid of creating the highway junctions which would not perfectly align the network.

  • This sounds like a short-term solution - is it valid to "get rid of" highway junctions that don't align perfectly? In reality, don't they exist - and if so shouldn't they be forced to align perfectly? Otherwise you're going to be suggesting non-optimal routes – Stephen Lead Aug 31 '16 at 0:31
  • The workflow is 1) create the network database; 2) select the highway from the network; 3) extract the highway junctions by using Intersect tool on highway and network junctions; 4) spatial join the highway junctions to the network junctions by setting very small tolerance (e.g., 0.00001 feet) to fix the imperfect alignment issue. 5) select the highway junctions from the spatial join table by choosing the field "count > 0". It works quite well for my case. Actually, this method also eliminates highway junctions are not real junctions since some of them are just vertices on the polylines. – Tianxin Li Aug 31 '16 at 1:58

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