A restow is a crane move that earns nothing: the box is lifted not because it has arrived, but because it is in the way. Every restow adds berth time, terminal cost and damage risk. This guide explains what causes restows, how to count them in a bay plan and how multi-port planning keeps them down. The basics of building the plan are in container ship bay planning.
What a restow is
There are two kinds of restow (often called shifting):
- Shifting on board: the box is moved to another slot on the same ship, in the same bay or a different one.
- Shifting via quay: the box is landed on the quay and reloaded once the boxes beneath it have been worked.
Both usually take two crane moves per container, and terminals normally charge them at different rates. In the BAPLIE message and terminal reports, a restowed box shows its old and new positions so the next port knows where it is now.
What causes restows
| Cause | Example | Prevention |
|---|---|---|
| POD sequence overstow | A Bitung box above a Makassar box in the same stack | Blocks per port of discharge, next port on top |
| Hatch cover overstow | Hold holds Surabaya cargo, deck above holds Makassar cargo | Deck cargo must leave at the same port as, or earlier than, the hold cargo below |
| Late or changed bookings | Late cargo squeezed into leftover slots, or a change of destination | Reserve slots for expected late cargo in the multi-port plan |
| Rotation changes | A port is omitted or two calls are swapped | Re-plan quickly from the latest BAPLIE |
| Weight and stability | VGM differs from the booking so a stack limit is exceeded, or GM needs fixing | Plan with VGM and leave a stack weight margin |
| Special cargo | A DG segregation conflict found late, a faulty reefer socket | Check DG and reefers before the plan is final |
Why restows are expensive
The cost of a restow is more than the tariff per move. It also hits:
- Crane time. As an illustration, if a crane averages about 25 moves an hour, 22 extra moves take almost an hour of crane time.
- Berth time and schedule. A delay at one port can ripple through the whole rotation.
- Extra hatch openings. Each hatch cover lift is a crane move with no cargo.
- Damage and error risk. Every extra lift is another chance of impact, lashing damage or a box in the wrong slot.
- Re-planning. Terminal and ship planners must update the plan and re-check stability.
Worked example: counting restows in one bay
Illustrative example. A small bay has 3 hold rows × 3 tiers and 3 deck rows × 2 tiers under a single hatch cover. The ship has finished loading at port A and then calls B → C → D. Letters in the table are discharge ports.
Plan 1 (port order ignored):
| Tier | Row 02 | Row 00 | Row 01 |
|---|---|---|---|
| 84 (deck) | D | C | D |
| 82 (deck) | C | B | D |
| Hatch cover | — | — | — |
| 06 (hold) | B | C | D |
| 04 (hold) | C | B | D |
| 02 (hold) | D | C | B |
At port B there is B cargo in the hold, so the hatch cover has to come off:
- Deck: five non-B boxes (C and D) must be moved. The B box in row 00 tier 82 is discharged.
- Hold row 02: B is on top and comes straight off, 0 restows.
- Hold row 00: one C above B, 1 restow.
- Hold row 01: two D above B, 2 restows.
That makes 8 restows at B, or about 16 extra moves, to discharge just 4 boxes. If the restowed boxes go back into the same stacks, port C still needs 3 more restows, because three D boxes on deck block the hatch opening. The total is 11 restows, and the hatch is opened at B, C and D.
Plan 2 (proper POD blocks), with the same 15 boxes:
| Tier | Row 02 | Row 00 | Row 01 |
|---|---|---|---|
| 84 (deck) | B | B | B |
| 82 (deck) | C | C | B |
| Hatch cover | — | — | — |
| 06 (hold) | C | C | C |
| 04 (hold) | D | D | D |
| 02 (hold) | D | D | D |
At B the hatch stays closed and all four B boxes are on top. At C the two deck C boxes come off, the hatch is opened and the three hold C boxes are on top. At D the rest is discharged. The result is zero restows and only two hatch openings.
| Measure | Plan 1 | Plan 2 |
|---|---|---|
| Restows at B | 8 | 0 |
| Restows at C | 3 | 0 |
| Extra crane moves | about 22 | 0 |
| Hatch openings | 3 | 2 |
Note that plan 2 puts all the D cargo at the bottom of the hold. If the D boxes are light and the B boxes heavy, stability or deck stack weight limits could become a problem. That trade-off is exactly what the planner has to balance.
Multi-port planning and optimizers
The restows above were easy to avoid because all the cargo was known. In practice a ship loads at many ports, and the B, C and D cargo is not all known when the ship leaves A. A good plan therefore looks at the whole rotation, not one port:
- Slot reservations per POD. Slots in chosen bays are held back for cargo expected at later ports, based on the carrier's forecasts.
- Hatch cover rules. Cargo loading at B for distant ports is steered to holds or bays where it will not block the hatch opening at C.
- Optimizers. Container stowage is highly combinatorial, so software uses optimisation algorithms to balance many goals at once: fewer restows and hatch openings, even crane work, while still meeting stability, strength, stack weight, DG and reefer constraints.
- Human review. Planners still check optimizer output, because some operational factors are not always captured by the model.
More detail is in multi-port stowage planning. To check POD order on real data, open a BAPLIE in the BAPLIE viewer; port order and distances can be checked with the port distance calculator.
A practical checklist for planners
- Sort the rotation and give every POD a colour before filling any slots.
- Check each stack from bottom to top: port order must never go backwards.
- For every hatch cover, compare the earliest POD in the hold with the latest POD on the deck above it.
- Count restows for every port, not just the next one.
- Keep spare slots for late cargo in bays where they will not block a hatch.
- After any restow, send an updated BAPLIE so the next port plans from the correct positions.
Where STOWAGE.ID fits
STOWAGE.ID Vessel Stowage counts overstows and restows per port for container ships, compares alternative plans and runs a multi-port optimizer from shore. It is planning and decision support; the vessel's class-approved loading computer and stability booklet remain the official reference for stability and strength. You can try the workflow in the demo.