Working to improve performance, comfort, health and safety at sea
Prof. Dr. Jelte Bos
Researcher at the Dutch Organisation for
Applied Scientific Research,
TNO, the Netherlands Organisation for applied scientific research, has performed extensive research on the subject of seasickness over the years. With the subsequent understanding of its causes and effects, Professor Dr Jelte Bos discusses the impact of seasickness on the maritime sector.
Using the term ‘sickness’ is a bit of a misnomer because the symptoms are not the result of a sickness. They are the normal reaction to abnormal conditions, to which almost all people suffer from to a certain degree,” states Professor Bos. “And it is important to note that symptoms are not all-or-nothing. The signs are gradual – starting with sweating, dizziness, burping, salivation or headaches. This can be followed by nausea and eventually vomiting.”
That dreaded feeling
Crucially, for offshore and maritime personnel, this ‘sliding scale’ of symptoms has a close correlation to work efficiency. “Our research shows that levels of performance are reduced if someone is suffering from seasickness. 60% of tasks just fail during periods of actual sickness. And a person who is not actually being sick can still have reduced levels of performance – with 20% of tasks failing in the early stages.”
These results are important from various viewpoints: “If a crew member is beginning to become nauseous, then it’s economically advantageous to prevent that. And, furthermore, performance is just one aspect of how we experience seasickness. This subject relates to comfort as well as key health and safety issues too.”
Time for acclimatisation
Human physiology can also have an influence on reducing the symptoms of seasickness. “Everything in the human body is directed towards adaptation,” he says. “In fact, everyone who has experienced seasickness knows that the first day is the worst. The second day may be a little better and the third day might be manageable. The human body is adapting. And there are many examples of this from human physiological research in addition to multiple anecdotes from maritime personnel,” explains Professor Bos. The human body’s ability to adapt is not unlimited though: “If your body has adapted to one type of movement and then you are exposed to a new type of movement, then you might develop seasickness from that. This might be valid, and indeed advantageous, for the permanent crew of a vessel, but not so beneficial for passengers such as offshore maintenance technicians who are transferred between locations on different vessels and do not have time to adapt.”
Although seasickness is a form of motion sickness (taking stimuli from the eyes and balance organs in the ear), it is also possible to experience it solely from visual cues. “This is called visually induced motion sickness – when people become nauseous or sick from movements that they see, not from movements that they feel.” Alternatively, this can be used to reduce the levels of seasickness of crews working below decks; a possible solution currently being researched is the introduction of a so-called artificial horizon that displays real-time Earth-referenced visual imagery. Although this is very promising, accuracy is paramount, says Professor Bos. “Even a delay as small as 200 milliseconds between the actual movement and the visual display can actually make things worse instead of better.”
Looking towards solutions to seasickness connected to ship design, the subject is complex. A vessel can move in no less than six different degrees of motion: referred to as heave, sway, surge, pitch, roll and yaw. This complexity is heightened due to the sheer unpredictability of the maritime environment. “While there is no single solution to cancel seasickness because it is caused by numerous aspects, TNO has data from 30 years of own research and more from others, particularly incited by naval operations during WWII. This gives us a better understanding about how ship movements influence seasickness.” And this is the connection between TNO and Damen:
We are working with Damen in an advisory role. I hope to be in close contact with the company so that, in an interactive process, we can decide on what can be done to reduce levels of seasickness in the future.
Graph adapted from BOS JE (2004). How motions make people sick such that they perform less: a model based approach. NATO RTO/AVT-110 Symposium on habitability of combat and transport vehicles: noise, vibration and motion. Prague, CZ, 4-7 October: 27.1-11.