Seems like a simple optimization on max tons/hr...however...

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03-22-2011 03:26 PM
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Hi there,

I have what seems like a relatively simple problem but there's a catch that I can't seem to figure out a workaround with Network Analyst.  Each road segment is coded with a maximum Tons/hr value.  If I maximize on this, It would generate the proper route that adds up all the segments of the route to give me the maximum tons/hr.  All roads are classified as either a 63.5 tons, 55.5 ton or 43.5 ton road.  If the route that is generated has any segments that would be 43.5 tons, then the whole route would need to be classified as a 43.5 ton road.

It's a bit confusing for me to try and maximize on tons/hr keeping in mind that if any of the segments have a lower ton rating, then all the segments would get tagged as 43.5 and the max ton/hr value would be much less.

Hopefully i've explained this enough for someone to try and understand.  Would greatly appreciate any feedback or ideas on this problem.

Thanks,

Nick
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Network Analyst finds paths my minimizing the cummulative path length.

Based on your description, I was not able to understan what you are trying to achieve.
Perhaps you can elaborate...

Jay Sandhu
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Jay,

Thanks for taking the time to look at my problem.  Let me try and be a bit clearer...

Currently we create optimal routes from multiple origins to multiple destinations optimizing on a least cost in minutes.  The need to provide routes based on payload (maximize Tons/hr) has become apparent.

A restriction exists whereby when optimizing on a maximum ton/hr, the least payload segment along a route, for example 25 tons, defines the entire route as such even though 90% of the route may be of 37 tons classification.   

This restriction requires the optimizer to consider all road segments along a path to validate the Gross Vehicle Weight (GVW) assigned to each arc and calculate the appropriate tonnage per hour for traversing that segment. This would all happen during the network analyst optimizer run so it would need to be dynamic, in such that if the algorithm were considering the next arc that would be added to a path had a higher weght capacity then it would need to adjust the tonnage assigned to the next arc to make it equivalent to the lowest weight assigned to any arc in the current path.  It would then need to evaluate the path against all other potential paths based on the objective function , maximize on tones per hour.

I hope this clears things up a bit...Please let me know if you have any questions.
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Nick,

You are trying to describe a behavior on how the solver should work to solve your problem.

But you are not describing your problem in detail. So I am going to guess that what you are trying to do is solve "The Transportation Problem". That is, you have a set of supply locations, a set of demand locations, capacity on the road network and the goal is to minimize shipping costs of moving a given amount of goods through the capacitated network.

If this sounds like what you are trying to do and you are not famillar with "The Transportation Problem", I would suggest doing a web search. A way to sovle it with linear programming is described here:
http://extension.oregonstate.edu/catalog/pdf/em/em8779-e.pdf

If this is what you were trying to do, then you can use the above methodology to use the OD Cost matrix to compute the travel costs, export them to an appropriate LP and solve. An example of this is here:
http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=C4E79AE3-1422-2418-88B2-008CC...

The above demonstrates how to use the LP approach for School allocation. You will have to modify it to solve your problem instance.

Regards,
Jay Sandhu
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Maybe I could paraphrase nickdemerchant's problem with the following example:

Two route options are available to transport goods from origin A to destination B.  The first route uses short-cut over a weight restricted bridge, takes 1.0 hours, and the truck can carry 25 tonnes of payload.  The second route avoids the weight restricted bridge, takes 1.25 hours and the truck can carry 35 tonnes of payload.  Which is the best route to take?

Using the least time method, you would select the first route as the best option.  However, given the increase in payload, the second option is the most effective route.  The first route delivers the goods at the rate of 25 tonnes/1.0 hours = 25 tonnes/hour.  The second route delivers the goods at the rate of 35 tonnes / 1.25 hours = 28 tonnes/hour.

Can route capacity (Gross Vehicle Weight) be accomodated by ArcLogistics when determining "optimal" routes?
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Can route capacity (Gross Vehicle Weight) be accomodated by ArcLogistics when determining "optimal" routes?


Yes. See the note on "Capacities" where it talks about Route properties.
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Vehicle_routing_problem_analysis/00470...


Jay Sandhu
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