We are solving route using published Network Analysis service in a US state.
Street network dataset is made from street centerlines and there is no z-value; however there are many overpasses and underpasses which do not intersect the main highways.
In a sample instance to explain the issue, we have a sign on the cross road (on the overpass) which is a restriction/barrier because sign's height is less than vehicle's height; so we select street segment related to sign which does not intersect the main highway but rather it is above the main highway (in 3D it does not intersect, but if you imagine in 2D it intersects).
When we try to solve the route in this situation, the section of main highway becomes restriction/barrier because it thinks that overpass is intersecting it.
How can we solve this issue either in the Network Analyst and/or with Data. We have whole state so there are several thousands of streets of all possible types.
Just to clarify, the restriction caused by the overpass sign is limited to just the overpass road itself (and not restricting the highway passing under it)?
Chris Donohue, GISP
Yes, the overpass road is selected as barrier but when it tries to solve the route, it brings main highway street segment in picture because NA thinks it is intersecting and hence even treat main highway's segment as restriction; hence solves the route incorrectly.
One thing we are planning to split the street segments so that it will not select larger street segment to avoid this situation, so that is at the data level but I am wondering whether something can be done at the Network Analyst level?
It is not clear from your description what problem you are running into.
For example, "the overpass road is selected as barrier".
How is the selection turned into a barrier? Are you using it as a line barrier? And that line barrier intersects with everything it crosses turning them into restrictions? In that case, you should be placing a point barrier on that overpass road.
You also mention that you have an overpass with a height restriction. Is it on that overpass, or is that overpass a bridge and the road underneath needs to be restricted due to height of bridge. If it is on the overpass, see above solution of using point barriers. You can use the GP tool Feature Vertices to Points and generate mid points on your overpass lines and use as point barriers. But do note that even if you generate a point on a road to place as a barrier, there is no guarantee that there is no other road underneath it at exactly that same mid-point (less likely but possible).
Perhaps posting a picture would help clarify the issue.