Delivery Time Windows and the Route Cost of Promises Made One Customer at a Time

Delivery Time Windows and the Route Cost of Promises Made One Customer at a Time

In most B2B distribution businesses, delivery windows are agreed in commercial conversations. A new account asks for an early delivery, an existing customer changes its receiving routine, a key account wants a guaranteed slot before opening. Each request is reasonable, and each is agreed on its own merits.

The transport team inherits the combined result. Every window becomes a constraint in the route plan, and the plan has to satisfy all of them at once. That is where the cost of a window appears: not when it is agreed, but when it meets every other window on the route.

A window has no cost of its own

Routing models represent an agreed delivery window as a time window on a visit, and this has been part of standard solution methods since the 1980s [1][2]. Seen through the model, a window does not add cost directly. It rules out some possible plans.

The cost of a window is therefore the difference between the best plan with it and the best plan without it. If the plan you would have run anyway still satisfies the window, the cost is zero. If it does not, the cost is whatever the next best plan requires: more waiting, a different sequence, longer driving, or another vehicle. The same window can be free for one customer and expensive for the next, depending entirely on what else is already on the route.

This is why window costs are so hard to see at the negotiating table. They are not a property of the request. They are a property of the plan the request lands in.

Define the window precisely

Agree whether the window refers to arrival, the start of unloading, or completion. For a pallet delivery to a store, arriving before 07:00 and finishing unloading before 07:00 can differ by forty-five minutes.

Keep receiving hours and agreed windows apart as well. A site may be able to receive from 06:00 to 14:00 while the agreement promises delivery between 06:00 and 07:00. The planning system needs the agreed window; the receiving hours are only the outer limit.

Finally, make sure the wording in the customer agreement and the value in the planning system describe the same event. Many service disputes start with a route that met the model and missed the promise.

A two-account example

Two customers, A and B, are 25 minutes apart. Each delivery takes 45 minutes to unload. One truck can carry both orders, and both sites can receive from 06:00.

With the standard window, the truck starts unloading at A at 06:00, leaves at 06:45 and reaches B at 07:10. Serving B first gives the same timing in reverse. With the early window, the second delivery starts ten minutes after the window closes.

This is a hypothetical feasibility example, not a simulation output or a customer result. Travel time is fixed and the depot leg is assumed to fit. On a real route these two drops would sit among many others, and the conflict could be absorbed elsewhere, or could ripple further. If neither window can move, the usual answer is a second truck or an earlier start, and both have a price.

How windows accumulate

No single window creates a problem. The difficulty is that windows are added one at a time, over years, by different people, and almost always in the same direction: earlier and narrower.

Each new early window competes for the same first hours of the day. Gradually the morning becomes the busiest period on every route, and the fleet ends up sized for the first wave rather than for the day. The trucks that make the 07:00 promises then sit underused by early afternoon.

Nobody decided this. It is the sum of many sensible decisions, each made without sight of the others, which is exactly why it is worth looking at deliberately.

Where we would start

Our recommendation
Make a standard delivery window the default in customer agreements, check the route impact before agreeing a narrower one, and review existing windows across the network once a year.

A standard default changes the starting point of the conversation. A narrow window remains available, but it becomes a deliberate exception rather than the norm, and the people agreeing it know that it is one.

The route check does not need to be elaborate. Re-plan three representative delivery days, including a busy one, with and without the requested window, and compare vehicles, driver hours and distance. If nothing changes, agree the window with confidence. If it adds a vehicle or a shift, share that number with the sales team.

The decision stays commercial. Some accounts are worth an extra truck in the morning, and a clear figure makes that an informed choice rather than a surprise for the transport team three months later.

The annual review applies the same idea to windows already in place. Relax existing narrow windows one group at a time in a re-plan, and see which ones change the number of vehicles needed. Often it is a small number of windows that drive most of the extra cost, and those are the few worth revisiting with customers.

Comparing window policies fairly

Use representative days, including a busy one. Keep orders, unloading times, vehicle types, working limits and travel times the same, and change only the windows under test.

Compare total cost, vehicles used, on-time delivery and unassigned orders together. A plan that looks cheaper because it drops difficult deliveries is not a fair comparison.

Separate firm commitments from preferences. A customer whose window exists because of a staffing pattern may be happy to move it by an hour when asked. A customer whose window reflects a store opening time may not.

How Optiyol fits

Optiyol’s B2B solution plans routes against customer windows, vehicle capacity and distribution requirements, together with the driver app and tracking [3]. Testing a requested window against a real day becomes a short planning exercise rather than an estimate, and the result can be shared with the commercial team before the agreement is signed.

A good place to start is one depot: list the narrow windows agreed in the last year, re-plan a few days with and without them, and see which ones the fleet is really built around.

Frequently asked questions

Do narrower windows always cost more

No. A narrower window rules out some plans, but the best plan may still be among those that remain. When it is, the window costs nothing.

Should sales stop agreeing narrow windows

No. Many narrow windows are justified by the customer’s operation or the value of the account. The aim is to agree them knowing their route impact, not to refuse them.

Are receiving hours and delivery windows the same thing

No. Receiving hours describe when a site can accept goods. An agreed window is the promise made within those hours. Planning needs both, kept separate.

Sources

[1] Solomon, M. M. (1987). Algorithms for the Vehicle Routing and Scheduling Problems with Time Window Constraints. Operations Research, 35(2), 254–265.

[2] Bräysy, O. and Gendreau, M. (2005). Vehicle Routing Problem with Time Windows, Part I: Route Construction and Local Search Algorithms. Transportation Science, 39(1), 104–118.

[3] Optiyol B2B delivery solution. https://optiyol.com/solutions/last-mile-b2b