Hi Heather, This solved my immediate problem but created more questions.
Below is a data table of resulting average travel times from the VRP solver. We are trying to create a tool that can help with different scenarios of paratransit ridership coupled with bus allocations (number of routes). The numbers derived here are the averages of the "TotalTime" values for each route. Something we noticed was that for lower ridership outputs we saw some type of solve instability whenever the number of seats surpassed the number of total riders. For example each bus has 14 seats, and as a result our results make sense when we get to 2 buses with 20 riders. When we get to 3 buses though, we essentially could have "1 extra" bus (as 2 buses could pick everyone up in one load). I am trying to understand conceptually why the average TotalTime could increase when 3 routes are assigned. I have tried a multitude of MaxOrderCount approaches including:
1. max(Orders/Bus_Count, BusCapacity)
2. max(Orders/BusCount, BusCapacity*.75)
3. Orders/BusCount
Is this a result of how the solver workers? Am I missing a concept? Do you have any ideas on what to check for that causes this instability?
These results are useful and give us a launching point for future analysis, but I am trying to understand this tools various parameters to determine what is relevant.
Thanks for your help so far!
David Wasserman, AICP