VRP that uses maximum allowed days

LouwrensCronje

Hello All,

Thanks for accepting me to the community. This is my first post - please be gentle!

I NEED YOUR HELP

I have the following scenario:

- One week to run a distribution for some goods

- Vehicles to start and end each day at the same depot (cannot take a break on route)

- StartWindowTime = 8am and EndWindowTime = 12pm i.e. 4hr available every day to deliver

- Each order point is only required to be serviced once

How do I configure my VRP in order to use the least amount of vehicles across the 5 days?

Regards,

Louwrens 

HeatherMoe

Hi Louwrens,

I think if your orders do not have any day of the week constraints and you are just trying to minimize the number of routes that are needed for this we can simplify your problem quite a bit by taking the "day" out of the planning process and deciding afterwards which routes will be run on each day.  

So for this on the orders you can just put the times (8am to 12pm) in without the date if using ArcMap or a GP tool to solve the problem.  If using a rest request then give all of the orders the same day and time when converting your problem to Milliseconds since epoch.  If the routes need to be contained within that same time frame you could even eliminate the order time windows all together and just rely on the start time of the route and the max total time values to restrict the work day to 4 hours.  Having the time windows is really just necessary if you allow the drivers some extra time to get from the depot to the first order or back after the last depot.  For example if they leave the depot at 7:30 and can get back at 12:30.

For the routes, put in essentially five copies of the routes that you have for one day.  So for example if you have 6 vehicles available to you, then you will put in 30 total routes in the problem.  If you are able to get vehicles on demand to be able to cover all of the orders then you want to make sure you have enough vehicles in the problem to be able to get to all of the orders.  For example if your drivers can get to 20 stops in a day and you have 600 orders, you would need a minimum of 30 vehicles in the model but to be on the safe side add a few extra.  The solver will naturally try to minimize the number of vehicles used but it does have a multi value objective with other costs such as time and distance so you can add a fixed cost to the routes which would make the cost of starting a new route more expensive and less likely for the solver to add unnecessary routes.  

This set up would divide all of the orders across the routes without regard to which day the route is to be driven.  Once you have the routes with orders, you can then decide which of them will be done on a specific day and divide the work across your five day time horizon.  

If I am missing a requirement for pre-specifying the day for routes then let me know and we can work through ways to get the problem to work.