Iceberg model · Four-day fleet trial
Will It Stop Again?
Fix today's broken van, and prevent the same failure moving to another van tomorrow.
The broken van is fixed. What about tomorrow?
The mountain van is already out of service. With only one maintenance bay, plan the next four days so the same failure does not recur in a different van.
Goal: complete at least 8 deliveries in four days, with no new breakdowns on the road. Vans already out of service must be repaired before dispatch.
Plan four days of maintenance ↓Already broken; needs repair
Dispatch adds further wear
Dispatch adds further wear
Try the original plan first, then compare whether failures recur across four days. Trials cost no resources; change the plan and retry anytime.
Which van stays for maintenance each day?
Each van completing its daily route counts as 1 delivery. Maintenance takes a day and resets wear to zero; other vans dispatch automatically. If wear reaches 6 after dispatch, the van breaks down and that trip does not count as delivered.
Route wear: mountain +2 / river +2 / city +2
Route wear: mountain +2 / river +2 / city +2
Route wear: mountain +2 / river +2 / city +2
Route wear: mountain +2 / river +2 / city +2
The scheduler's policy
After changing policy, compare using the same schedule. Changing a slogan alone may not make maintenance happen.
Servicing a healthy van leaves only two for dispatch. “At least 3” cancels preventive maintenance; a van already broken can still be repaired.
Open handover notes and old policy
- Previous Monday: the mountain van reached wear 6 and stopped.
- Previous Tuesday: the mountain van was repaired; the river van broke down on the road.
- Previous Wednesday: the river van was repaired; the city van broke down on the road.
Assumption behind the old policy: “Servicing an unbroken van wastes a dispatch opportunity.” The old schedule only called for maintenance after failure.
This is a documented management position in this case, not a guess about staff's thoughts based on one breakdown.