Counting the number of barriers the routes of an OD Matrix pass through

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06-13-2011 09:54 AM
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New Contributor
Hello,

I'm pretty new to Network Analyst, but am trying to come up with a way to get Arc to count the number of potential "points of conflict" the routes of an OD Matrix pass through. I have these "points of conflicts" stored as a feature class points layer, and each point falls exactly at the intersection of the lines in my single line road network feature class.

I've found I can sort of do this using "Accumulation Attributes" (working my "Points of Conflict" feature class into the network, then using it as a cost with a constant value of "1"), in which case, Arc reports the number of points in the final ODlines table.

However, I'm having a problem where a lot of my points are coming up as "standalone junctions", because Arc does not place a junction point everywhere there is a possible conflict.

I'm wondering if (as an easy way around the standalone junction problem) there's some way I could just load these points as "point barriers" and have the OD Matrix report on those (or count them as accumulation attributes), but I can't find any way to get this to work.

Any suggestions would be greatly appreciated!
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Hello. I saw in your other post that you said the following:
When I did the build of my network dataset, it did not put a "ND junction" point at all these points (and I can't see any pattern in where it opted to put one vs. not put one). Any of my "POC" points that are not coincident with the ND junction points produces a standalone error.


What this tells me is that the points you are creating and that are giving you the stand-alone error aren't truly coincident with the endpoint/vertex of a line. Try zooming in really close, I don't think the problem junctions you created will be coincident with the ND_junctions (AKA "system junctions"). In fact, Network Analyst shouldn't create a system junction on top of user-defined junction.

Try these steps as a test:
1. Start an edit session to edit the junctions you created.
2. Add the snapping toolbar and turn on all snapping except for edge snapping.
3. select one of your problem points with the Edit Tool.
4. Drag it so that it snaps to the system junction that appears to be on top of it.
5. Stop editing and save your edits.
6. Build the network.
7. Create a route and see if you get the expected results.

Please let me know if that was the issue or not.

Thanks,
Robert
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Hi Robert,

I had created all my points using "feature vertices to points", and had further checked their XY coordinates against the sketch properties of my lines, so I was pretty certain this wasn't it, but it turns out it was! Thank you so much for your help. I've been working on this all day - I thought the problem was something else because the Arc-generated junction points disappeared seemingly at random - since this was my first time using network analyst, I didn't realize that the junction points wouldn't show up once my conflict points were correct. (Which still strikes me as weird, but everything is working, so it's good enough for me!)

Thank you again!!
Amber
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