This question already has an answer here:
Although reasonably experienced with ArcGIS I am a bit of a newbie with Network analyst. I have a situation in which things work Ok with the tutorial data but not with mine!
I am trying to determine an 8km road distance from a set of hospitals in East Africa. I have some roads data that I can build into a network. As far as I can see there is full connectivity. If I work using detailed polygons (which is what I want) I get this.
So the "service area does not go along roads A,B and C, which I would expect it to. and how on earth does it think I am going to get to Point D!!.
Using generalised polygons I get this:
Now I have lost the slightly anomalous point D, but the services area still does not traverse roads A and B.
I am using ArcGIS 10.2 for Desktop.