Closest Facility - stay only on one road?

[AdamMcArthur2]

I currently have a problem getting the desired result out of network analyst.

The project:
I'm doing an network analysis of the interstate system in the state of michigan to determine the number of exits 20 miles upstream and downstream of each rest area in the state. I have a network dataset built for the roads, and shapefiles for rest area and exit locations.


Currently I'm using closest facility to determine which exits are near the rest areas (within 20 miles). My problem is that I cannot get network analyst to only look at the road that the facility is on. For example: I have a facility located on I-75 in Detroit. When I run the closest facility analysis, it finds routes 20 miles upstream and downstream on I-75, and every other route on the network within the 20 mile allowance (I-94, m-10, I-96..etc).

Is there an easy way to write a script or use restrictions to keep the analysis on the road the facility is on?

Any help is appreciated.

-Adam

[JoeBorgione]

I currently have a problem getting the desired result out of network analyst.

The project:
I'm doing an network analysis of the interstate system in the state of michigan to determine the number of exits 20 miles upstream and downstream of each rest area in the state. I have a network dataset built for the roads, and shapefiles for rest area and exit locations.


Currently I'm using closest facility to determine which exits are near the rest areas (within 20 miles). My problem is that I cannot get network analyst to only look at the road that the facility is on. For example: I have a facility located on I-75 in Detroit. When I run the closest facility analysis, it finds routes 20 miles upstream and downstream on I-75, and every other route on the network within the 20 mile allowance (I-94, m-10, I-96..etc).

Is there an easy way to write a script or use restrictions to keep the analysis on the road the facility is on?

Any help is appreciated.

-Adam

Why not build a network based on just those segments that are I-75? 

Select from your full feature class RoadName (or what ever) = I-75.  Then do a spatial selection for roads the intersect the select I-75 segments.  that ought to get you your ramps and rest areas.  If you get any extras, like over passes, just unselect them.  Export the ones you keep to a feature class and build your I-75 network.