Hierarchy and Restrictions

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06-09-2011 06:27 AM
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New Contributor
Hi! all,
I hope I get some insight on this...
Given everything else constant, if a network does NOT have a hierarchy built, does the closest facility that gets picked gets picked on the basis of 'Restriction'?

I noticeed that a route was created for a closest facility in my network (without hierarchy) that veered from the feeder road (with restriction) for a short distance (along a small loop of minor road that is two way, and without restriction) only to continue on the feeder later. Feeder has higher speed while the minor road has lower speed. There is no connectivity problem nor there is a 'direction digitized' problem on the portion of route that was not chosen.

Thank You,
Shilpa
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Shilpa,

From your description it sounds like a correct path was found by avoiding a restricted portion of the road by travelling on a minor road for a short distance. Not sure I understand what is the problem in this case.

The closest facility picked is the closest in terms of your impedance attribute honoring all the network settings in terms of restrictions, turn impedances, barriers, etc. If it is not picking the closest, then can you post more details?

Jay Sandhu
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Hi! Jay,
Yes, your understanding is correct. I had asked for 6 closest paths to be computed to an incident from 20 facilities. This particular route was the third closest based on time it takes to traverse. But it could have been the second closest path if it had not veered from the path simply on the basis of restriction, as there was no other reason for it to veer. This makes me believe that I have to use hierarchy if the goal is to be very accurate for finding all 6 closest paths by rank.

Thanks Jay,
Shilpa
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Esri Regular Contributor
Shilpa,

Hierarchy is a concept that support very fast long distance routing. It is not guranteed to find the most optimal path.

If you are using Closest Facility solver in a small regional area you should not use hierarchy.

That said, I do not understand your issue. If you have a restriction, it will be honored regardless if the hierarchy is used or not. By defination, a restricted edge can not be traversed by the route solvers. You can remove it if you do not think it is required for your particular situation.

Perhaps you can explain what you are trying to achieve.

Regards,

Jay Sandhu
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