A warehouse runs on slots. A slot is a 30-minute window in which a carrier is expected to arrive, dock, and unload. Slot compliance is the percentage of arrivals that hit their slot. A warehouse running at 80% slot compliance is operating. A warehouse running at 60% is in chaos.
The chaos is not the warehouse’s fault. It is the cost of running on tools that do not talk to each other. The warehouse knows its slot schedule. The carrier knows their ETA. The shipper knows neither. The slot slips because nobody sees the slip coming.
Why slots slip
A slot slips for one of three reasons:
- The carrier is late. The truck is stuck in traffic, or the previous load ran long, or the driver is on a mandatory rest break.
- The warehouse is late. The previous truck is still in the dock, or the dock crew is on a shift change, or the forklift is down.
- The slot was wrong. The shipper booked a 30-minute slot for a 60-minute load, or the carrier accepted a slot they could not make.
In all three cases, the slip is predictable. The carrier’s ETA was wrong two hours before the slot. The warehouse’s dock backlog was visible three hours before the slot. The slot’s mismatch was obvious at booking time.
Why the spreadsheet does not fix it
The standard fix is a shared spreadsheet. The shipper writes the slot. The carrier writes the ETA. The warehouse writes the dock status. Everyone reads.
The spreadsheet breaks down for three reasons:
- It is not real-time. The carrier’s ETA updates every 15 minutes. The spreadsheet does not.
- It is not authoritative. The shipper’s slot, the carrier’s ETA, and the warehouse’s dock status disagree. The spreadsheet does not resolve the disagreement.
- It is not actionable. A slip on the spreadsheet is a fact, not a trigger. The dispatcher has to read the spreadsheet, see the slip, and decide what to do.
What the control tower does
The control tower treats the slot as a data object, not a row in a spreadsheet. The slot has a start time, a duration, a carrier, a warehouse, a shipment, and a status. The status is computed from the carrier’s ETA, the warehouse’s dock backlog, and the slot’s duration.
When the status slips, when the carrier’s ETA falls outside the slot, or the warehouse’s dock backlog pushes the start time past the slot, the control tower fires an event. The event is routed to the dispatcher, with a suggested next action: rebook the slot, reroute the truck, or escalate.
The takeaway
Slot compliance is not a scheduling problem. It is a data problem. The data exists, in the carrier’s telematics and the warehouse’s WMS. The fix is to put the data in one place, compute the status, and route the action. The spreadsheet was never going to do that. The control tower does.