The scenario is that there are points on a grid with intervals of 1000m covering an area of hundreds of square kilometres. I want to find routes on a road network to any one of these points. A road network built with Network Analyst works fine and the points are also built into the network. However the points do not intersect with the roads and sometimes offset 10s to 1000s of metres so no solution/route can be found to these points.

How can routes be solved to the closest part of a road nearest to these points if they are loaded as stops?


In ArcGIS Network Analyst, during the add locations procedure (for any kind of locations, like stops or barriers), you can set:

  1. The search tolerance, that limits the distance from the location point to network lines for network analyst to consider them valid;
  2. And the Snap to position along line, that will move you point to the nearest network element.

I believe that setting generous search tolerance (the size of your grids?) might solve your problem, yet, notice that if a point is too distant from the network, the chosen nearest network element might not be the most accessible, therefore check your results before using them. If that happens you might move your points a bit, or add a valid point that you know it will be more accessible to the pretended one.

Update: Another option, would be to improve your network for those specific cases\areas (e.g. add unpaved or footpath roads that connect to your point).

  • Thanks Alexandre, the default search tolerance was 5000m and that was ample for most of the points. Initially, I tried to add locations from a purpose built feature classes of a few selections in ArcMap in order to select just a few locations from about 980 in a 900 sqkm area also including Snap to position along line but nothing worked even though the points appeared to be intersecting the network. So I rebuilt the network and choose to add selected points from active layers in ArcMap and got some solutions. Still trying to get solutions of inputs from non active layers.
    – Rod
    Jun 26 '13 at 9:38
  • This is somewhat strange, but try to put all your layers in the same projection system. Sometimes, network analyst can be very picky about it. Good luck Jun 27 '13 at 8:46
  • Putting all my files into the same projection system is one of the first thing I do on any project. That's not an issue. At the moment selected points from active layers in an open ArcMap window are snapping to closest road point and creating routes. However, when trying to add points from a file in the catalog and not from an active layer, the points are added but don't snap to road and so the route has errors.
    – Rod
    Jun 29 '13 at 5:57

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