A rational approach for reduction of motion sickness & improvement of passenger comfort & safety in sea transportation

Studies previously conducted in laboratory and field environments have produced a method for predicting the discomfort caused by multi-axis vibration at frequencies between about 1 Hz and 100 Hz, with some useful information at frequencies down to 0.5 Hz. However, knowledge of the discomfort response at lower frequencies is limited, especially the manner in which discomfort caused by roll and lateral (or pitch and fore-aft) oscillation combine to cause discomfort. Results of laboratory studies performed with the COMPASS project will be used, with previously published data, to develop a method of predicting subjective responses arising from discomfort caused by fore-and-aft, lateral, roll and pitch oscillation at low frequencies. Results of recent motion sickness research conducted to investigate the frequency-dependence of motion sickness caused by roll (over the frequency range 0.025 to 0.4 Hz) and horizontal oscillation (over the frequency range 0.0315 Hz and 0.20 Hz) will also be re-interpreted so as to provide frequency weightings for predicting effects of horizontal and rotational motions.

Ship designers, operators, and classification societies recognize the positive impact of comfort requirements on the overall well-being of passengers. To provide criteria that will assist in improving comfort of passengers onboard passenger vessels, classification societies have been developing guidelines with the objective of defining comfort requirements for passenger ships. There are five categories of comfort criteria that may be controlled, measured and assessed in passenger spaces on vessels: accommodation design, indoor climate, lighting, noise, and high and low-frequency whole-body vibration. Low-frequency whole-body vibration is caused by ship motions, and these ship motions induce motion sickness, fatigue, and a degradation of motor tasks. Because of the complexity involved, the assessment of low-frequency whole-body vibration has, until now, not been considered. To overcome this difficulty, criteria based on rational standards are needed for assessing low-frequency whole-body vibration relating to passenger comfort on board ships. Results of Task 5.3 will consist of rational standards for human comfort on board ships. Such standards serve to establish prenormative guidelines for rule development, specifying rating levels of acceptability. The following categories of passenger motion comfort are to be defined: pleasant, acceptable and uncomfortable.

These guidelines, have provided the most essential information, experience and tips to produce the best design as well as for operational matters from the motion sickness and passenger comfort point of view. Guidelines have covered Cruise and passenger ships as well as HSC in relation to operational decisions such as weather routing, comfort improvements during the operation as well as engineering assessment, internal design for passenger comfort and maximum earning capacity. The compass results have improved their cruise vessels, HSC and Ropax designs and order books. As a consequence, integrated design tools and design guidelines in relation to passenger comfort are the ideal end products for European shipyards.

The COMPASS results have improved cruise vessels, HSC and Ropax designs and order books. Particularly integrated design tools and design guidelines in relation to passenger comfort are the ideal end products for European shipyards. There are many European designers and consultants serving to the shipping industry and both operational and design tools will be very beneficial for their designs and engineering services. In addition, the compass partners will provide their expert services to designers and consultants as specialist services.

The experience and know-how gained through the Project will be consolidated in a standard methodology to evaluate comfort on board of sea-going ships. A permanent long-term monitoring system will be installed on-board consisting of a set of accelerometers, a wave meter and a PC unit. The PC unit will serve for data acquisition as well as data processing by means of dedicated software. The software will include the enhanced comfort model output from the Project, which will be fed by the suitably processed acceleration signals. The system will be able to continuously monitor the local and overall comfort levels on board of the ship. The correlation between the estimated comfort levels and the corresponding recorded operative conditions (speed, wave height) will allow the ship operator to refine the operational guidelines to the Captain from the point of view of comfort.

Market reviews and surveys were carried out on board of Cruiser ferries, Ropax vessels, Mono hull High Speed Craft, Catamaran High Speed Craft in different geographical areas, namely the Baltic Sea, the Norwegian Sea, the English Channel and the Mediterranean Sea. These questionnaires have provided valuable information on how to identify the important parameters on motion sickness, passenger comfort and how to deal with these issues using technical and operational approaches. Three separate surveys and reviews area were carried out on: Passengers, Crew, Operators. The questionnaires provided very valuable information on Passenger Comfort, earning capacity and passenger preference as well as design and operational issues from the Passenger, Crew and Operators perspective. In addition the reports also include the methods of dealing with passenger comfort problems including technological and operational approaches.

In the series of simulator trials in WP4.1, 28 subjects were exposed to low-frequency sway and heave motion, and combinations of both. The purpose was to investigate perceived comfort and motion sickness as a function of motion magnitude, as well as the interference of ship motion with passenger activities. To this end, we used the TNO ship motion simulator, a sea-container with inner dimensions of (L x W x H) 3.8 x 2.2 x 2.4m, mounted on a piston of 2.5m above the roll and pitch axes based in a gimbals system. Maximum roll and pitch angle is limited to +/-15°, respectively +/-20°. The gimbals system could additionally be translated vertically with a stroke of 1 m. The motions were controlled by a hydraulic system. Eight artificial motion profiles were used, ordered in a Latin square design to account for randomness and a balanced order of conditions. A total of eight motion conditions was the maximum that could be carried out during one day. As described below, subjects performed four different tasks during each trial, according to a rotating scheme. During each trial only one of the eight motion conditions was presented. For several reasons a simulator trial should not exceed 15 minutes, and each trial consequently comprised of four periods of three minutes: two minutes of which was reserved for the execution of a task (see below), and the remaining minute was reserved for filling in a task-related questionnaire. During each motion condition, subjects were asked to perform a set of psychomotor tasks that encompassed a range of passenger-related activities aboard ships. Passenger activities were divided in five categories: - Cognitive activities, - Physical activities, - Recreational activities, - Provocative activities, and - Eating and drinking. The first three categories (cognitive, physical, recreational) were explicitly covered in experimental tasks that were performed during each motion condition. Cognitive aspects were examined in a reading task that also involved some arithmetic. Physical aspects were investigated in a manual task (writing), and in a locomotor task (walking). As recreational activity a dart game was employed. The effects of head movements were examined implicitly during a letter acquiring task. The order of the tasks was digram balanced to avoid order effects. Instead of investigating the disturbing effects of ship motion on eating and drinking during all eight motion conditions, this was done during separate lunch and coffee breaks inside the simulator using a motion profile with increasing amplitude over time. It may be noticed, that sleeping and resting is not listed in the essential passenger activities. For practical reasons this was considered beyond the scope of this study. Comfort was rated in three ways: - Objectively by rating task performance (e.g. the number of missteps during the walking task), - By means of task specific questions answered just after each task, and - By means of a general questionnaire just after each trial. A total of 1120 questionnaires were returned in this trial. Within-subject analyses of variance (ANOVA) were used to analyse the data statistically. Separate tests were used to analyse for effects of sway only, heave and sway in combination, and the regularity of sway motion. The results showed that sway motion affected comfort more than heave motion, and that the effects of both motion components added linearly. Performance on motor tasks was impaired during motion, in contrast to the performance on cognitive tasks, which was hardly affected. For all activities, however, perceived effort increased considerably with increasing motion amplitude, even though the performance itself did not always suffer from the motion. Since also motion sickness symptoms increased with motion amplitude, an important conclusion is that subjective ratings discriminate more than objective scores. The general questionnaire revealed that comfort ratings were strongly related to discomfort ratings, and that all mental and physical comfort parameters behaved in a similar way. This leads to another conclusion that, principally, discomfort can be described by one general subjective rating. However, the results indicated that in an operational questionnaire special attention should be given to aspects of enjoyment, fatigue, motion sickness, and postural balance. Three subjects had to quit the experiment due to motion sickness, which implies a motion sickness incidence of 10%. The findings of this study are of relevance for the design of questionnaires to be used in the sea trials (WP2 and WP3), and to quantify the overall relationship between comfort and ship motion (WP5).

The sea trials data collected is being used for improving sea-sickness model. The model is based on mathematical description of human vestibular system. The model has been incorporated in software called ShipComf (Alpha version at this stage). The software model would be integrated within VRSHIP Technology Platform. The model has been described in publicly available conference papers.

The experience and know-how gained through the Project will be consolidated in a standard methodology to evaluate comfort on board of sea-going ships. A permanent long-term monitoring system will be installed on-board consisting of a set of accelerometers, a wave meter and a PC unit. The PC unit will serve for data acquisition as well as data processing by means of dedicated software. The software will include the enhanced comfort model output from the Project, which will be fed by the suitably processed acceleration signals. The system will be able to continuously monitor the local and overall comfort levels on board of the ship. The correlation between the estimated comfort levels and the corresponding recorded operative conditions (speed, wave height) will allow the ship operator to refine the operational guidelines to the Captain from the point of view of comfort.

Passenger services were improved all around on the basis of the results of the modelling tool and the use of onboard integrated passenger comfort tools for ship operations. This combined software/hardware tool is a combined system integrating the motion sickness assessment software and the on board measurement systems which provides an onboard continuous measurement of the ships motions, vibrations, temperature, air quality as well as the observation/prediction of motion sickness/passenger comfort on various locations of the ship board. The system also includes decision support systems (developed within COMPASS) for the captain to take right actions to reduce the discomfort. The motion sickness and passenger comfort model is integrated with hydrodynamic and design tools and it provides a unique environment to assess and optimise the design with reference to motion sickness and passenger comfort. Because of the integrated optimisation, the best overall performing design can be selected very quickly. It is an ideal tool for design activities of consultants, designers and shipyards. New Motion Sickness and Passenger Comfort standards are human orientated and designed specifically for sea transportation and valid for wide range of vessels including Cruise Vessels, Ropax, Mono and multihull HSC. It is believed that these standards will lead the industry to a different era and Classification Societies, health and Safety Executives as well as IMO will be targeted to introduce these in the marine regulatory framework.

During the design process of a new high speed vessel you always have to go several rounds through the well known design spiral towards your final goal. It is a fine balance between the importance of the different ship parameters and the possibility to achieve your wanted demands. It is a trade off situation and you have to weight the pros and cons of your eventually decisions. This means that you have to study how you in the best possible way can incorporate the main comfort parameters like lighting, temperature, noise, vibration and motions in the ship design. If you achieve a good combination, you will have satisfied passengers and a crew that have the best possible starting point to take care of the passengers.

The experience and know-how acquired in the Project will be consolidated into a comfort-oriented ship design methodology. The methodology will consist of general guidelines as well as of an integrated software which will allow the designer to automatically optimise the hull forms from the comfort point of view taking into account the design constraints as well as additional objective (i.e. the calm-water performance). The methodology will be used to support ship designer in the definition of the main parameters at the preliminary stage as well as to increase quality / number of consultancy / research activities.

SES has through a 6 years period worked with research and development on a new high speed vessel concept, called Air Supported Vessels (ASV). One main issue has been to improve the passenger comfort compared with state of the art high speed vessels. The COMPASS project has therefore been a great opportunity to gain important experience and know-how about comfort problems on common high speed crafts. With this important knowledge about comfort problems, it has been easier for SES to integrate this parameter in the design process.

The main task of WP3 was to gather data regarding comfort of passengers on ships at sea by means of questionnaires and measurements. At the end, the data were complete of 4 ships, two large monohull cruise and two catamaran fast ferries, having made 33 trips, yielding a total of 3150 returned questionnaires. As a first step in charting comfort as a function of ship motion and other environmental factors, the questionnaire data have been analysed without making reference to ship motion and other environmental factors in WP5.1. It was the aim of this study to 1 - determine the most important effects observed (which may be of importance to specific operators, for example), 2 - to settle which discomfort entities should be analysed in WP5.2 regarding the recorded ship motion and environmental measures, and 3 - to determine how these discomfort entities should be adjusted for age, gender, and other factors, thus minimising the variability in predicted versus observed comfort values when taking motions into account in addition (WP5.2). To that end, frequency tables were presented, and we looked for effects other than what might have been expected by mere coincidence using appropriate statistical tools (2 tests). These analyses were constrained to two-way interactions. These analyses showed that the discomfort entities illness, unsteadiness, satisfaction, and sleep disturbance behaved more or less independent, and/or were expected to behave differently depending on ship motion and the other recorded environmental factors. Of these four factors, only illness was significantly dependent on age, gender, and sickness history. The COMPASS data showed a clear relationship that could be used to quantify these latter effects with a minimum of parameters. This result was judged to be of interest to a broader public, why a manuscript on this topic has been submitted to the European peer reviewed journal Ergonomics. The three main conclusions from this task were that: - Seasickness was the most obvious factor contributing to passenger discomfort aboard ships, - Illness (seasickness) should be adjusted for age, gender, and sickness history, before being used to analyse the effect of ship motion in WP5.2, - Other factors that should be taken into account, besides seasickness, are unsteadiness, satisfaction, and sleep disturbance, and these factors do not require further adjustments for age, gender, etc.

SES had initially planned to do the sea trials onboard their Air Supported Vessel (ASV) prototype, but because of some unfortunately delays in the building process, they had to look for an alternative solution. SES will therefore first perform some sea trials onboard a conventional high-speed catamaran, and later perform the trials onboard the ASV prototype. The first sea trials onboard a conventional catamaran (apporx 40m LOA) will take place in April 2004, and will be carried out on the west coast of Norway. The vessel is operation between Trondheim city and Kristiansund. The vessel has a seating capacity of approx. 280 passengers. The passengers include comuters, tourists and occasional travellers. SSRC in collaboration with other partners have created a comfort data sample for a 177m long conventional cruise ferry operating in the Baltic Sea between Stockholm and Helsinki. The distinguishing features of this dataset is the simultaneous measurement of physical parameters (global ship motions, local vibration and noise) and human response; relatively long stay of passengers on the ship; balanced sample of passengers with respect to gender and age. The database comprises of response from 1333 passengers collected from 4 voyages of 16-hour duration. The dataset covers detailed record of global ship motions over the entire journey. The local vibration measurements (covering a wide spectrum of DC-130Hz) provide a representative coverage of the whole ship over different journeys. Noise levels in the vessel are derived from several local noise measurements distributed over the entire vessel.

A realistic and human orientated motion sickness and passenger comfort model was used. Two types of modelling was adopted. The first one was based on the statistical approach using the full scale trials, lab results and theoretical modelling. In parallel other models were developed by individual partners using sensory conflict theory and human vestibular systems. The model is based on the Full Scale Trials and Lab /Simulator results, passenger surveys as well as the previous studies in this field and medicine. The model covers motion sickness, passenger comfort, postural stability, fatigue, cognitive and motor tasks. The full scale trials provide significant input to the understanding of motion sickness and passenger comfort phenomena and the development of the mathematical model, guidelines and standards. Full scale trials provide the following interrelated data on High Speed Craft, Ropax Vessels and Cruise vessels. Results from Simulator and Lab trials: these are complimentary to full scale trials to fill the gap and to obtained more detailed results that can not be obtained from full scale trials. These trials are done under controlled environment and provide very be crucial data on the effect of individual parameter or task on the passenger comfort and sickness. The data includes the effect of individual/ combined motions and various amplitudes on motion sickness, and some task performed by passengers like walking, standing, manual tasks and reading. Furthermore, the Lab data extends to effect of frequency and seat characteristics.

Anticipating increasing demand for cruise ships in the coming years and to consolidate in ferry market IZAR has decided to develop new design and construction ideas. The ferries built by IZAR are leading-edge products that meet the strictest international comfort and safety standards for passenger transport vessels, but current standards can be improved. The results of this project will be used to develop new design tools and methodologies to carry out innovative comfort oriented ship design. With this innovative solutions It is expected to gain capacity in providing solutions that could be of interest not only to the traditional Shipowner, but also to companies which luxury and speed have become decisive factors.

Experimental studies are being performed to extend current knowledge of the fundamental relationships between low-frequency motions, discomfort and interference with activities of passengers and crew. Discomfort caused by low frequency motion is particularly important because it can occur even when other effects are not present (e.g. there is no interference with activities or motion sickness) and because there is currently very little knowledge of how to predict discomfort caused by low frequency translational and rotational motions such as may occur on fast vessels. The specific aims are to investigate the response of seated and standing persons to motions in four axes: ry (pitch), x-axis (fore-and-aft), rx (roll) and y-axis (lateral). These studies encompass motions at frequencies between 0.2Hz and 1.6Hz, and include consideration of the influence of postural support, especially backrest support. The results will be used to allow comparison of absolute levels of discomfort between ry (pitch) and x-axis (fore-and-aft) response, and between rx (roll) and y-axis (lateral) response, and to provide information for extending the frequency weightings used in current methods for evaluating ride comfort so as to encompass low-frequency ship motions.

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