Pickers in a busy warehouse can walk 15–20 kilometres a day. Significant distance savings can be obtained by carefully choosing the sequence the items are picked in, and in how large orders are split into individual pick-routes.
We ran a study to find out how much of that distance could be cut using modern optimisation algorithms, without changing the warehouse layout, staffing, or any physical infrastructure.
This research was conducted as part of the OWL project. At Solwr, we have built these findings into our WMS. If you want to explore what this could look like for your operation, reach out to our team.
Orders are typically split into pick-routes based on fixed rules:
These rules are applied sequentially, and the resulting routes are then handed to the routing step. The two problems are never solved together.
Most WMS platforms route pickers using a tag-based policy: each warehouse location has a tag, and the picker visits locations in tag order. It is simple and consistent, but it does not account for the actual walking distance between locations. For example, a picker might need to walk an entire corridor to pick the next item in the sequence, rather than picking it later when they can take a shortcut and walk only half of said corridor.
The new routing algorithm treats each pick-route as a variant of the classic traveling salesperson problem (TSP). It:
Building a distance matrix for a large warehouse is computationally expensive. To solve the optimization problem, one needs to build a large matrix with hundreds of thousands of distances for a large order. This can take hours with standard distance computations.
The study used a reduced graph model — a simplified representation of the warehouse's corridor structure — which brings full matrix construction down to a few seconds. This makes real-time deployment feasible, with the caveat that corridor renaming requires a manual update to the model.
Order splitting is how a large order gets divided into several pick routes. Most warehouse systems split orders using fixed rules such as weight and volume limits, weight classes, temperature zones and location groups. Because this happens separately from routing, the routes that result are often longer than they need to be.
No. Route optimisation works within your existing layout and racking. Layout does affect how much can be gained, but no physical changes are required.
Changing the location assignment can have an impact on the picking distance, but the algorithm optimises for your current assignment, without changes needed.
To optimise splitting and routing, the only data needed is a representation of the relative distances in the warehouse, and the position of the pick locations. If it is important for your application that items are picked in a given relative order, then the optimisation algorithm uses that information too.
