How many terminal tractors does a quay crane need?
A quay crane can only work as fast as tractors arrive under it. Each terminal tractor, also called a yard truck or tugmaster, drives a container between the crane and the yard block, waits for the yard crane or reach stacker, and comes back. If its round trip takes six times as long as the crane needs to serve it, the crane needs six tractors to keep working without a pause.
The calculator works out the tractor cycle, the tractors one crane can keep busy, the match factor of the tractors you assign, the crane moves per hour and shift that follow, and the yearly fuel cost of tractors idling with the engine on.
Why does the tractor count matter?
- Too few tractors: the crane stops between boxes, so the ship stays longer at the berth.
- Too many tractors: tractors queue under the crane with engines running, burning fuel and driver hours.
- Distance changes the answer: a vessel at a far berth or a yard block at the end of the terminal lengthens every cycle.
- Idling is most of the day: NREL's study of yard tractors at the Port of New York and New Jersey recorded 4.7 idle hours in an average 8-hour run day.
What inputs do you need?
| Input | Where to find it | Tip |
|---|---|---|
| Crane cycle per move | Crane logs, terminal operating system reports, a stopwatch | Loading and discharging differ; use the operation you plan for. |
| Time under the crane and at the yard | Observation, tracking data with geofences at the crane lanes and yard blocks | Record a full shift: yard waiting changes with the block. |
| Distance and speed | Terminal layout, tractor tracking data | Use the average speed driven, not the speed limit. |
| Working minutes per crane-hour | Gross and net crane hours in vessel reports | Net ÷ gross × 60 gives the figure. |
| Engine hours and idle share | Hour meters, the tracking system's idle report | Take a full month, all shifts. |
| Fuel per idle hour and diesel price | Engine data, fuel records, the official pump price | Measured idle fuel is better than a published average. |
How is the tractor count calculated?
Tractor cycle and tractors per crane
This is the balance between a loading unit and its hauling units, Equation 4-16 of the King Saud University course on loading and hauling: hauling unit cycle ÷ loading time, rounded up. Here the quay crane is the loading unit and the tractors are the hauling units.
Match factor and crane moves per hour
A match factor of 1 means neither waits; below 1 the crane waits for tractors; above 1 tractors queue under the crane, as defined in the match factor literature (Journal of Mining & Environment, 2025). Crane moves per hour here follow TIC 4.0's gross productivity idea of moves over the hours the crane is ready to work, reduced by the working minutes you enter.
Idle cost
Sources
- King Saud University, CE 419, Chapter 4: Loading and Hauling, part 3 (Equation 4-16: hauling units per loading unit). Source: KSU.
- A. Bartosiewicz & A. Kucharski, The Determination of Times of Transhipment Processes at Maritime Container Terminals, TransNav, Vol. 16, No. 3, September 2022 (quay crane cycles of about 85.7 s loading and 101.5 s discharging; one quay crane worked with five internal vehicles). Source: TransNav.
- A. Kotz, K. Kelly, D. Gagne, B. Oakleaf (NREL), Port Authority of New York and New Jersey Yard Tractor Electrification Study, data of October–November 2018, presented to AAPA in November 2019 (8 run hours and 4.7 idle hours a day on average). Source: NREL / AAPA.
- U.S. Department of Energy, Argonne National Laboratory, Long-Haul Truck Idling Burns Up Profits, August 2015 (about 0.8 gallon an hour idling a heavy truck). Source: U.S. DOE.
- TIC 4.0, Productivity Gross KPI definition (moves ÷ logged hours), version 20240412. Source: TIC 4.0.
- M. Mohtasham, Development of a Match Factor for Optimizing Haulage Fleet Efficiency, Journal of Mining & Environment, 2025. Source: JME. Last reviewed 21 October 2026.
Worked example: two cranes and ten tractors
The defaults are examples; replace them with your terminal's figures.
- 600 m at 20 km/h takes 1.8 min each way. With 1.5 min under the crane and 4 min at the yard, the tractor cycle is 9.1 min, 40% of it driving.
- At 100 s a move the crane needs 1.67 min per tractor trip, so one crane can keep 9.1 ÷ 1.67 = 5.5, or 6 tractors, busy.
- Two cranes with 10 tractors give a match factor of 0.92: the cranes wait 8% of the time. The tractors feed each crane 33 moves an hour against a crane capacity of 36; at 50 working minutes that is 27.5 moves an hour per crane, 440 moves in an 8-hour shift. With 11 tractors the crane becomes the limit at 30 moves an hour.
- Ten tractors running 8 engine hours a day with 59% idle stand 47.2 hours a day with engines on. At 3 L an hour for 360 days that is about 51,000 L a year, $24,468 at $0.48 a liter; cutting idle time by 30% saves about $7,341.
How to read your results
- Match factor below 1: tractors are the limit. Add tractors, use a nearer yard block or cut yard waiting before asking the crane to go faster.
- Match factor above 1: the crane is the limit and tractors queue. Move tractors to another crane or reduce the gang.
- Travel share: when driving dominates, the yard plan (which block receives each vessel's boxes) matters more than tractor speed.
- Idle share: idle hours count on the hour meter too, so they bring services forward.
How to cut tractor waiting and idling
- Rebalance gangs by distance: assign more tractors to cranes whose yard blocks are far away.
- Measure the cycle: geofences around the crane lanes and the yard blocks give each tractor's entry and exit times.
- Set an engine-off rule for long waits, and follow idle time tractor by tractor.
- Service by engine hours: plan services from hour meters with the Preventive Maintenance Schedule.
- Know the hourly cost: work out what a tractor hour costs with the Equipment Hourly Cost Calculator.
Assumptions and limits
The calculator uses averages: every tractor has the same cycle and arrivals are evenly spaced, so real queues are longer when cycles vary. One crane serves one tractor at a time, and each tractor serves one crane. It does not plan crane sequences, dual cycling or the yard plan, and it does not read crane or terminal operating system data. All defaults are examples, not equipment or terminal data. Use the result to plan and compare, then confirm it with measured cycles.