Hierarchy Problem - No Solution Found

115
10
11-14-2012 02:34 PM
Highlighted
New Contributor
Hi,

When I have Hierarchy option enabled, I get an error "No Solution Found". Without Hierarchy, it works fine. There are 6 road classes, Hierarchy worked fine when I had Road Class 1-2 combined as Primary Highway, Road Classes 3-4 combined as Secondary Highway, and 5-6 as Local. When I changed Primary Highway from 1-2 to 1-3, rebuilt the dataset and ran the solution, I got an error. Any idea why is it happening?
Thanks in Advance.

R.
Tags (2)
Reply
0 Kudos
10 Replies
Highlighted
Occasional Contributor II
Does that mean you also changed the next class as 4 to 6 ? i think the hierarchy values should not overlap.
Reply
0 Kudos
Highlighted
New Contributor III
So, if I'm understanding you correctly, in the table for the Hierarchy, you have a range of numbers, but it seems one of them over lap.  With using Hierarchy, they cannot overlap.  It's also easier to have less classes of roads.  For instance a 1 for all primary, 2 for secondary, 3 for third traveled and 4 for the least or locals.  At least this is what I found out when I use Hierarchy.  Hope this helps.
Reply
0 Kudos
Highlighted
New Contributor
Thanks Nicole and SK,

The values don't overlap, I don't think it is possible in ArcGIS or even logical to overlap the values. I assigned 1 to 3 values to Primary Roads instead of 1 to 2. Secondary Roads have value of 4 and Local Roads 5 to 6. I hope it makes sense now. There shouldn't be any problem with this change but not sure what is going wrong.

R.
Reply
0 Kudos
Highlighted
New Contributor III
Can I ask why you have three different values for one set, and two for another?  That seems excessive.
Reply
0 Kudos
Highlighted
New Contributor
The dataset I am using has Road Class from 1 to 6. Currently, I am using 1 to 3 for Primary, 4 for Secondary, and 5 - 6 for Local.

Previously, I was using 1 and 2 for Primary, 3 and 4 for Secondary and 5-6 for Local but figured out that 3 also represents major roads. It was working fine until I changed Primary from 1 to 2 to 1 to 3.

R.
Reply
0 Kudos
Highlighted
Esri Regular Contributor
Most likely the streets coded as level 1 to 3 are not fully connected. According to the online help at:
http://resources.arcgis.com/en/help/main/10.1/#/About_network_analysis_with_hierarchy/00470000005700...
It states:[INDENT]If the highway is disconnected, the route solver does not descend to the local street and connect. Instead, an error is returned. ArcGIS assumes that the highest order of hierarchy is connected.
[/INDENT]

Also note that hierarchy is useful for long distance routes in very large networks. If you do not have a large street network then you should not add or use hierarchy.

Jay Sandhu
Reply
0 Kudos
Highlighted
New Contributor
Thanks Jay. Any suggestion on how to check  and make connectivity of hierarchy?
Reply
0 Kudos
Highlighted
New Contributor III
On way is to do a Service Area with generating LINES not Polygons.  Make the break large, like 30 miles or so, and it'll show you where the disconnect is.
Reply
0 Kudos
Highlighted
Esri Regular Contributor
You can do a couple of things:

Select only the streets for levels 1 to 3. Create a feature layer from the selection. Now symbolize each layer with different color and see if you can visually see some gaps between the lines

Use Nicole's suggestion, but first write out the selected level 1 to 3 lines to a new feature class, make a network on it and then run the service area for a large value with the Lines option (not polygons). Does the service area cover all the lines?

Jay Sandhu
Reply
0 Kudos