Container ports: reconcile crane lifts, boxes and TEU
A port can handle more TEU without lifting more boxes, and it can move more boxes without making the same number of crane hoists. Container size and twin lifting change these relationships. Research should reconcile all three units before interpreting a productivity improvement or estimating equipment utilisation from annual throughput.
The deliverable is a call-level work log that separates boxes, twenty-foot-equivalent units, physical hoists and time. It is an accounting model for operating evidence, not a crane operating plan. All numerical records below are fictional and do not represent a port in the cited performance index.
Locate the index definitions
The World Bank’s Container Port Performance Index 2020 to 2024 defines crane intensity, gross crane hours and moves in the glossary on PDF page 11, printed page xi. In that glossary, container moves include discharge, restowage and load, while hatch covers and non-container work are excluded. The cargo-operations discussion on PDF page 46, printed page 30, describes twin lifting.
These definitions make the scope of a comparison inspectable. They do not mean a physical hoist is always one reported container move. The index’s methodology also considers ship and call characteristics; it should not be read as a standalone ranking of a single crane’s mechanical speed.
Obtain the terminal event log, container-size codes, load/discharge/restow flags, twin-lift flags and per-crane time records. Match the vessel call and cutoff in every feed. Annual throughput, a quay-crane trial and ship time at berth are different evidence objects and cannot be divided together to create a measured hourly rate.
Rebuild boxes and TEU
Assume a single call unloads six hundred twenty-foot boxes and four hundred forty-foot boxes. Define the twenty-foot boxes as one TEU each and the forty-foot boxes as two TEU each for this simplified mix. Total discharged boxes are one thousand and total discharged TEU are 600 + 400 × 2 = 1,400.
Among the twenty-foot boxes, two hundred are handled as one hundred twin lifts. The remaining four hundred twenty-foot boxes and all four hundred forty-foot boxes use eight hundred single lifts. Physical hoists total 100 + 800 = 900, while container moves for the defined unloading task remain one thousand.
| Unit | Calculation | Total |
|---|---|---|
| Boxes | 600 + 400 | 1,000 |
| TEU | 600 × 1 + 400 × 2 | 1,400 |
| Twin hoists | 200 boxes ÷ 2 | 100 |
| Single hoists | Remaining boxes | 800 |
| Physical hoists | 100 + 800 | 900 |
Average boxes per physical hoist are approximately 1.1111. Average TEU per box are 1.4. These ratios describe the task mix, not a universal crane conversion. The worksheet excludes other container lengths, hatch-cover handling and restowage at this first step.
Reconcile the time denominator
Assume four cranes are each assigned to the call for twenty-five hours on the defined gross working-time basis. Total gross crane-hours are one hundred. The call’s corresponding operating interval is twenty-five elapsed hours, giving crane intensity of four under these assumptions.
Using the same one-hundred-crane-hour denominator, productivity is ten boxes per crane-hour, fourteen TEU per crane-hour and nine physical hoists per crane-hour. These are different rates derived from the same observed task; none should be relabelled as the other.
Dividing by twenty-five elapsed hours instead gives forty boxes per elapsed operating hour across all four cranes. That system rate is not the rate achieved by each crane. Multiplying forty by four again would count concurrency twice. If the full berth stay is thirty hours, unloading boxes divided by the berth stay is approximately 33.33 per elapsed berth hour, another different scope.
Assume the one hundred gross crane-hours contain twenty crane-hours of documented stops. Net active time is eighty. The net active box rate is 12.5, versus the gross rate of ten. The difference comes from the time boundary. It does not demonstrate an improvement unless both comparison periods treat stops consistently.
Test size mix without claiming equipment improvement
For a separate task with the same one thousand boxes and one hundred crane-hours, suppose the mix becomes four hundred twenty-foot and six hundred forty-foot boxes. TEU rise to 1,600, so TEU productivity rises to sixteen. The box rate remains ten even before considering how physical hoists are arranged.
The TEU increase therefore does not prove faster box handling. It is a size-mix change. To attribute a capital investment’s effect, compare boxes, hoists, elapsed time and size mix on matched calls, or explicitly adjust for the changed workload. Empty and laden boxes should also remain identifiable; identical TEU do not establish identical cargo revenue or handling conditions.
Add restowage on its own work line
Return to the original unloading case and add twenty container restow moves during the call. Under the report’s stated move definition, these contribute to the call’s container-move count. They do not become twenty additional imported boxes delivered to the terminal customer population.
Keep discharged cargo, loaded cargo and restow work separately before forming a combined move numerator. If the additional restows are twenty single hoists, physical container hoists become 920. Whether a source reports each restow event differently must be checked in its data specification; do not impose this example on an undefined terminal series.
Hatch-cover or other non-container work may consume crane time even where excluded from the move numerator. Record its time and the applicable gross/net rule. Deleting that time from only the later period can create an apparent productivity gain with no change in actual service delivered.
Check the slowest work assignment
Suppose a different call assigns four hundred boxes to one crane and two hundred to each of three others. If each can complete ten boxes per active hour under the simplified assumptions, the first assignment requires forty hours and each other assignment twenty. Averaging the total workload over four cranes would suggest twenty-five hours, but the unequal work split does not support that elapsed completion time.
This arithmetic identifies a scheduling boundary; it is not an instruction to operate cranes differently. Actual feasibility depends on vessel arrangement, access and the terminal’s constraints. Obtain the real assignment and event records before equating total crane-hours with the elapsed time customers experience.
Use the call verification sheet
| Input | Obtain | Check |
|---|---|---|
| Container units | Size and empty/laden codes | Boxes not substituted for TEU |
| Work type | Discharge, load and restow events | Cargo throughput distinct from repeated work |
| Hoists | Twin/single flags and crane logs | Physical lifts distinct from container moves |
| Time | Per-crane start, stop and finish | Gross/net, assigned/active and overlap |
| Call duration | Vessel milestones | Crane-hours distinct from elapsed berth time |
| Comparison | Matched ship and call characteristics | Index score not treated as one crane’s speed |
When totals disagree, reconcile duplicated scans, restows, cutoff timestamps, size codes and non-container work. Preserve the event identifiers and a named residual rather than forcing TEU to equal boxes. A missing twin-lift flag makes hoists unknown even if container totals are reliable.
Update after corrected event logs, changed time rules, mix revisions or new call data. The conclusion should identify which numerator and time denominator actually improved, and whether the evidence concerns equipment work, vessel service or aggregate port performance.
Reproduce the event population before trusting a dashboard
Link every counted box movement to a timestamp, container identifier, work type and crane. A duplicated scanner message can inflate moves without another physical hoist. A missing message can create the reverse gap. Keep corrections as auditable event changes rather than altering only the final total.
The declared twin lifts in this example pair two twenty-foot boxes; there are enough such boxes in the original six-hundred-box population. A summary with no size or twin flags cannot establish the nine-hundred-hoist result merely because it reports one thousand boxes. Preserve the compatibility of the event population instead of inferring equipment capability from an average.
For a commercial comparison, request the terminal’s charging units separately. A crane-hoist count, reported TEU and invoice line can have different scopes and prices. The operating log does not establish revenue by itself. Keep empty/laden, transshipment and customer-contract distinctions visible before translating a work-rate improvement into a financial assumption.
Net inventory flow is also not gross work. A separate call unloading one thousand boxes and loading one thousand can have little net change in terminal box inventory while completing two thousand box movements. Add the loading events and relevant time to a new work ledger rather than use the zero net inventory change as crane workload.
FAQ
Is one TEU always one box or one crane lift?
No. Box size and multi-box hoists break both equivalences.
Can a port index be used as a single-crane speed ranking?
No. The index and a crane-level work rate have different scopes and controls.