Humans, operating and riding High-Performance Marine Craft (HPMC) in rough seas at high speeds require high level of performance capability. In his licentiate thesis, Pahansen de Alwis at KTH, Royal Institute of Technology, writes, "it is worth considering that even though the designers develop unbreakable craft, they are operated by the humans with fragile structures".
High-Performance Marine Craft (HPMC) is a complex man-machine system demanded with high level of performance, not only the craft but also the personnel aboard. These craft are often deployed by navies, coast guards, customs, marine pilots, special military operations and rescue units for maritime interdiction and intervention, seizure operations, search and rescue, rapid insertion and extraction of crews and surveillance.
Day and night, they are demanded to operate these craft at high speed in rough seas to accomplish their missions. The High-Performance Marine Craft Personnel (HPMCP), i.e. crew and passengers, aboard these craft often wear heavy operational equipment, including body armour, helmets and sometimes night vision goggles.
Vibration and repeated shock
Operating and riding a HPMC under these circumstances leaves the personnel vulnerable to many psychophysical consequences. A consistently identified fact is that the exposure to work environments containing vibration and repeated shock elevates the risk of adverse effects on human health and performance, which is also true for HPMCP. There are many HPMC deployed in the field and many personnel work aboard these craft and many more to come.
Therefore, in his research, Pahansen de Alwis and his research colleagues have developed a method to continuously analyse the exposure conditions aboard HPMC in order to feedback the crew indicating the risk of acute injuries due to severe impacts and the risk of adverse effects due to accumulated vibration exposure.
Then web-based questionnaires have been developed, validated and reliability tested in order to survey the health and working conditions of HPMCP.
Why do we know so little about this area? Human factors and HPMC?
- If you look at human factors, there are many studies about human factors but mainly on ergonomics perspective. Studies related to human performance are also now coming up but related to health are lacking. For health aspects, epidemiological data is required. It could be either registry data or data collected via surveys. Lack of epidemiological data limits the knowledge in this area, Pahansen de Alwis says.
The questionnaire tools have also been tested in a pilot study on a set of military seaborne personnel. During eight weeks, craft acceleration and GPS data was recorded by vibration measurement systems installed on board four HPMC while work related exposure, health and performance data was collected using the web-based questionnaires.
Even though data is limited, the results of the pilot study indicate a considerable level of pain incidence and high level of vibration exposure, exceeding the upper limit for the lifetime exposure as recommended in ISO2631-5:2004. This confirms that there is a relationship between vibration exposure and the health impairments in personnel aboard HPMC.
Further, a cross sectional study has been conducted on the personnel of the Swedish Coast Guard. Data from 342 coastguard officers shows that musculoskeletal pain and mental fatigue are prevalent among the study population. Musculoskeletal pain prevalence is comparatively higher than that of the general population and similar populations signifying the consideration of the human factors in terms of health and performance in HPMC design and operation.
What has surprised you in your findings?
- One important observation was that there are visually identifiable trends in the correlation between subjective and objective work exposure. It was also observed during the pilot test that most of the time the daily vibration exposure is above the daily vibration dose levels recommended in the ISO standards as well as EU legislations, although the seaborne personnel have been exempted from EU legislation limit values. Another interesting observation, during the pilot study, was that the navigators' acceleration levels are higher than that of the drivers', Pahansen de Alwis says.
The research will now be continued with further collection of data from the Swedish Coast Guard in order to get sufficient subjective and objective data about work-exposure, health and performance of HPMCP. The aim is to identify and quantify exposure-effect relationships facilitating better use of the existing standards, supporting ongoing development of the existing standards and providing information to draw appropriate design and operational limits in rules and regulations.
How do you want your work and findings to be used in the future?
- The method for real-time crew feedback system can be used to inform HPMC crews about their exposure conditions during regular high-speed operations in terms of the risk of adverse effects on human health and performance. So that the craft operators can take necessary actions to reduce the risk, Pahansen de Alwis says.
- Once the relationships between the working conditions aboard HPMC and the adverse effects on human in terms of health and performance are quantified, the acceptable levels of vibration exposure for HPMCP can be drawn. Therefore, design and operational limits can be decided upon.
- When the factors affecting human health and performance due to working conditions aboard HPMC are found, required design changes can be made at the design phase and preventive actions can be taken in the operational phase. This is valid for the quantification of the exposure-effect relationships too.
Therefore, Pahansen de Alwis sees the following steps:
- Finally, we need to establish the balance between the craft’s ability and the human’s capability to make the most out of the technical resources, i.e. a balanced man-machine system, Pahansen de Alwis says.