How many vehicles do I need to solve my VRP?

How do I use Nextmv to determine the size of my vehicle fleet? As in, how many vehicles do I need?

This is where some simple scenario testing comes in handy and is easy to do with Nextmv. Most operations determine fleet sizes with the goal of ensuring all stops get serviced. Put another way, you want enough vehicles so no stops get unassigned — otherwise there’s a lot of unhappiness: customers don’t get what they want and drivers get stretched too thin.

The best way to do this, in my opinion, is to start by generating a few input files for a given region that differ only in the number of vehicle values you provide. Perhaps you’ve got 20 vehicles to start, run that file, and look at the number of unassigned stops. If there are any, keep upping the number of vehicles in your input file until all stops are assigned. Once you see all stops get assigned, you’ve found a good fleet size.

Check out this video for more detail using the Nextmv Routing app:

In practice, when doing this for more than just a few scenarios, you’ll likely want to automate the process of generating input files and running them using Nextmv with a simple script. Internally we have several tools for doing this and are looking to make them available to our users as well.

For an example script and a preview of how we might approach the problem of fleet size at a larger scale, check out this video: