Why Speed Trials Matter More Than Anyone Admits

On a chosen day off the coast, a brand-new ship runs a measured course a dozen times or so, in both directions, at several power settings. The whole exercise takes a day or two. The numbers it produces will be argued about, relied upon, and quietly inherited for the next twenty-five years.

That asymmetry, days of measurement, decades of consequence, is the first thing to understand about speed trials. The rest of this course is about making the days good enough for the decades.

What the trial establishes

The deliverable is one object: the ship's speed-power relationship in calm, deep, still water at a stated loading condition: the curve that says, at this delivered power and this draught, the ship makes this speed through the water.

Three different audiences take that curve and stake something on it:

The builder and the owner settle the newbuilding contract on it. Ships are sold with guaranteed speeds at specified power and draught; shortfalls carry penalties, and serious shortfalls carry rejection clauses. The trial is where the guarantee meets the water.

The regulator reads it through the efficiency indices. EEDI (for newbuildings) is computed from the ship's speed at a reference power, a number established and verified through trial analysis; EEXI (for the existing fleet) uses the trial curve where one of that grade exists, and an approved estimate otherwise. The trial thus quietly became a compliance instrument: get the analysis wrong and the ship's regulatory efficiency rating is wrong with it.

The fleet's future analysts inherit it as the performance baseline. Every in-service speed-loss figure the ship will ever produce (the machinery of our ISO 19030 course) is a comparison against this curve. An error in the trial propagates, invisibly and permanently, into every number downstream.

Why a standard, and which documents

Here is the structural problem: the trial is run in the real ocean, wind, waves, current, finite depth, while the deliverable is defined in an ideal one. Bridging that gap takes corrections, each one a model, each one moving the final number. And the parties around the table have opposite interests in which way it moves: a wave correction chosen generously helps the builder clear a guarantee; chosen stingily, it helps an owner argue a penalty.

ISO 15016 exists to take that choice off the table. It standardises the whole analysis: what conditions a trial may be run in, what must be measured and how, and exactly which corrections are applied by which methods. Its companion is the ITTC's recommended procedure for speed/power trials (7.5-04-01-01.1, revision 08 of 2024), the towing-tank community's openly downloadable version of the same aligned methodology, and this course's standing open reference. (The ISO standard itself is a paid document. Its regulatory standing is on the public record in two IMO resolutions: MEPC.261(68), which in 2015 endorsed ISO 15016:2015 for EEDI trials from 1 September 2015, and MEPC.403(83), which in April 2025 named ISO 15016:2025 and the 2024 ITTC procedure as the EEDI reference, with the 2015 edition accepted only for trials before 1 May 2026.)

The standard's answer to the conflicting-interests problem is worth stating plainly, because it is the same answer ISO 19030 gives to in-service disputes: fix the method before the measurement, and the argument moves from arithmetic to facts. A witnessed trial analysed per the standard can still be argued: was the sea state really within limits?, but the argument is about checkable conditions, not about whose spreadsheet wins.

The shape of the course

The course follows the trial's own chronology. Preparation (lesson 2): condition of the ship, choice of site, the limits on weather and depth that decide whether the trial is winnable at all. Conduct (lesson 3): double runs, steady approaches, what is actually measured. Then the correction chain in three parts: current and wind (lesson 4), waves (lesson 5, including how a research formula became part of the standard), shallow water and loading (lesson 6). Finally the synthesis: from corrected runs to the delivered curve and the trial report (lesson 7), and what changed in the standard's 2025 edition, plus how to read any trial report critically (lesson 8).

One habit to carry through: the trial is a measurement under adversarial conditions: commercially adversarial, meteorologically adversarial. Every rule in the standard exists because someone, somewhere, once had a reason to bend exactly that part of the process.