Starting 1 May 2026, all EEDI-relevant speed trials must be conducted according to ISO 15016:2025 or ITTC Recommended Procedure 7.5-04-01-01.1
“Preparation, Conduct and Analysis of Speed/Power Trials”, 2024. From that date, ISO 15016:2015 will no longer be accepted as a valid reference. Discover more about the revised speed test regulations in this statutory news.
Background
The ISO published a revised edition of the “Specifications [formerly Guidelines] for the assessment of speed and power performance by analysis of speed trial data” in 2025. This version was adopted as the new reference for EEDI speed trials by MEPC.403(83).
Improvements to the correction methods
The overarching principles of the new standard remain consistent with the 2015 edition, which was introduced following the IMO’s implementation of the EEDI scheme. The newly introduced 2025 revision focuses primarily on refining specific methodological details to enhance the accuracy, robustness and comparability of speed trial results. With the new ISO 15016:2025, amendments to the following correction methods have been implemented:
1. Wind correction
The maximum wind speed during the speed trials is newly defined and depends on the ship length. Besides that, two different curves are determined in order to give an incentive for advanced sensors. The application of the fixed installed cup-type anemometer is still possible, but in this case the maximum wind limit becomes more stringent.
The wind profile has been updated: from a power 1/7 function, which is usually applied onshore, to an exponent of 1/9 with a steeper profile that better matches offshore wind.
Additional wind resistance coefficients for modern ship profiles (e.g. twin-island container ship) are provided.
2. Wave correction
The choice of the wave correction method is restricted, with a clear priority sequence:
(a) When wave height and direction are measured, transfer functions from the seakeeping model tests, or, if not available,
(b) the newly introduced SNNM method can be applied. This semi-empirical method combines the additional resistance from wave reflection and ship motion in the waves, similar to STAWAVE 2, but also includes a term to consider the wave direction related to the ship heading.
(c) If there are no measurements of the wave conditions, but only visual observation of the waves is carried out, the usual correction method is the STAWAVE 1 method.
(d) Only if significant pitching or rolling of the ship in the waves occurs can the SNNM method be applied with a theoretical wave spectrum.
The STAWAVE 2 method has been removed from the standard, along with the NMRI method. However, STAWAVE 2 can still be used when following the ITTC guideline.
A simplified measurement of the wave conditions has been introduced. Before and after the speed trial, a wave buoy is dropped from the ship and drawn back with a line.
3. Shallow water correction
The Lackenby method from 1963 has been replaced by the Raven method. The Lackenby method overestimated the shallow water impact, as it was based on former hull forms. The Raven method usually gives smaller corrections.
It is important to note that the upper limit of the application of the shallow water correction has been removed, meaning that the Raven method always applies. In deep water, this method provides only a minor correction, but in intermediate water depths in which the shallow water correction was not valid up until now, corrections will now slightly improve the result.
4. Water temperature correction
The roughness allowance has now been included in the correction in agreement with the correction that is applied for model tests.
5. Curve fitting
The calculation is more straightforward, with one calibration factor averaged from the relation of model test prognosis and the corrected speed trial value for each power setting.
Different results for sister vessels with the same measurement values
The updated correction methods will change the results for upcoming sister vessels or when re-evaluating previous tests:
The new wind profile will usually slightly increase the wind correction, particularly for container vessels with the anemometer located on top of the high deckhouse.
The water temperature correction will also typically increase the result when the water temperature is above 15°C during trials.
The shallow water correction in intermediate water depths will change the result, with the same tendency to higher results.
With the change from the 2015 to the 2025 revision, an increase of the results for the same measured values can usually be expected in the range of 0.0 to 0.2 knots. Only when the shallow water correction was applied for the 2015 version must smaller corrections and lower results now be expected.
Assessment of the changes
The new revision provides incentives for the application of advanced measuring devices, such as:
- For advanced anemometers, namely ultrasonic sensors or lidar, a higher maximum true wind speed limit is acceptable, which provides additional flexibility to the schedule of the trials.
- The application of additional ultrasonic wind sensors for the short-term application during the trials means only minor additional effort. There is no need to replace the fixed installed cup-type anemometer, but the advanced sensor can be mounted temporarily for the trials.
- Lidar systems will remain an exemption for trials, although recommended for trials to verify the performance of windassisted propulsion systems.
- The use of a wave buoy allows for the application of the SNNM method instead of STAWAVE 1. Calibration data of the buoy must be provided to the EEDI verifier.
- An improved comparability of the results is included in the new revision:
- The priority sequence for the wave correction provides clear selection criteria, so that the same method will be applied in an independent evaluation of the measured data.
- If no wave measurement is available, but visual observation has been applied, a verification of the ship’s movement in the waves is required. This can be provided by a short video; a measurement of the bow acceleration is not required anymore.
- The SNNM method can be applied in the case of ship motion occurs and wave measurement is not carried out. In this case, the SNNM method can only refer to unidirectional waves. A Pierson–Moskowitz spectrum is generated according to the visually observed significant wave height, mean wave period, and wave direction. Due to the restriction to unidirectional waves, swell cannot be included in this consideration. Only in case of wave measurements, both swell and wind waves might be considered.
- With the broader application range of the shallow water correction, attention must be paid to the determination of the water depth, particularly for intermediate water depths.
Recommendations
- Avoid referencing outdated ISO standards in contracts and documentation.
- Use an additional anemometer connected to the data acquisition system and position the sensor away from structural disturbances.
- Deploy a wave buoy, which enhances both accuracy and confidence in wave assessments.
- Several software tools are available for data evaluation, such as STAIMO, iSTAP and ProSTA.
- If you need support for speed trials, DNV Envilab will help you with sea trial planning, as well as performing and evaluating measurements on board. It provides its own solution for ISO 15016:2025 measurement equipment and software for evaluation. DNV Envilab also offers the application of lidar for trials with wind-assisted propulsion systems.
Robban Assafina is now on WhatsApp channel. Click Here
