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‘On 99% of the voyages, a reduction in lashings can be achieved using our WDL method, without compromising on the safety of crew, vessel and cargo.


Weather Dependent Lashing (WDL) is an innovative methodology that enables ship operators to reduce the number of unnecessary lashings during voyages with favorable weather conditions. The prescribed number of lashings in the Cargo Securing Manual (CSM) is sufficient for navigating through extremely adverse weather conditions.

With the availability of modern weather forecasts, it is now possible to continuously monitor and predict weather conditions worldwide.

Therefore, excess lashings are no longer needed when the upcoming weather will be favorable.

Siri Marine has developed a unique and Class-approved Weather Dependent Lashing system that assists the ship Master in selecting the optimal lashing plan for each voyage. This system enables ship operators to reduce the number of lashings while maintaining the necessary level of safety.


The procedure involves installing a Siri Marine Decision Support System on the vessel to record motion data. The measured accelerations are combined with the actual wave heights to create a matrix of forces versus wave heights for different weather conditions. This provides an insight into the seagoing behavior of the vessel, and based on this, three lashing schemes are defined: light, heavy, and IMO CSM lashing. For each lashing scheme, the required amount of lashings for various cargo positions is calculated.

This leads to the creation of a ‘WDL manual,’ which is a documentation package containing the outcome of all lashing calculations approved by Class. By using WDL, the forecasted wave height for the upcoming voyage determines the applicable lashing scheme. Ship-specific handouts provide an easy-to-use overview of the required amount of lashings for various cargoes.

The WDL system reduces unnecessary lashings, enhances operational efficiency, and improves safety during voyages with favorable weather conditions.



The utilization of the Siri Marine WDL approach can yield noteworthy reductions in lashings. The accompanying figure illustrates a customized lashing arrangement for several cargo types and various lashing schemes, obtained from the WDL methodology.

The figure demonstrates that by implementing the WDL system, notable reductions in lashings can be attained in comparison to the conventional IMO CSM lashings.


Fig. 1: Example of a ship specific lashing scheme.

On 99% of the voyages, a reduction in lashings can be achieved using the Siri Marine WDL method, without compromising on the safety of crew, vessel and cargo.

Upon analysis of voyages completed by ships equipped with the Siri Marine WDL system, it has been found that a vast majority of voyages (86%) utilize the light lashing scheme, with the heavy lashing scheme being used on 13% of voyages. The CSM prescribed lashings are only necessary on 1% of voyages throughout the year. This indicates that the Siri Marine WDL method can achieve a reduction in lashings on 99% of voyages without compromising the safety of the crew, vessel, and cargo.





Fig. 2: Percentages based on measurements over the year 2022.


Siri Marine has been developing and implementing the WDL methodology since 2003, and in recent years, more than 75 RoRo vessels have been equipped with a Siri Marine WDL system. As a result, Siri Marine is currently the world's largest supplier of WDL systems for RoRo vessels.

The Siri Marine WDL system is tailored to the specific needs of each ship, resulting in the highest possible lashing reductions while still ensuring the safety of crew, vessel, and cargo. The WDL manual provided by Siri Marine is applicable for worldwide trade and is based on extensive in-service monitoring.

Investing in the Siri Marine WDL system has a rapid return on investment, typically in six months or less. Additionally, this system reduces wear and tear on lashing equipment, saves on stevedoring costs, reduces crew workload, and shortens turnaround times in port.

The system also allows for slow steaming, resulting in reduced fuel consumption and CO2 emissions. Furthermore, the live monitoring of ship motions increases safety for crew and cargo.


on the spot

1 system =
8 sensors & 6 virtual

post processing data available
25- 200 Hz

  1. Ship specific WDL system; ensures highest achievable lashing reductions

  2. WDL manual applicable for worldwide trade

  3. Based on extensive in-service monitoring

  4. Return on investment in 6 months or less

  5. Reduce wear and tear of lashing equipment

  6. Save on stevedoring costs

  7. Reduce crew workload

  8. Shortened turnaround times in port

  9. Allows slow steaming, reduced fuel consumption and CO2 emissions

  10. Increase safety by live monitoring ship motions

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