Does Size Matter?

Last month, on Friday 13th, almost exactly 100 years after the sinking of the Titanic, the Costa Concordia cruise ship hit well-charted rocks off the coast of Italy and sunk, with the loss of at least 17, and perhaps as many as 32, lives. While those of a superstitious ilk might be pondering otherworldly causes for this tragic coincidence, those of us who have seen a modern cruise ship up close may be thinking along more technical lines: namely, how on earth do those things float in the first place, and is it really that surprising when they sink?

At nearly 1000ft long, and with a gross tonnage of 114,000, the Costa Concordia was over twice the size of the Titanic and was the largest passenger vessel ever to flounder. (And yes, past tense is now appropriate according to the ship’s underwriters). Perhaps unsurprisingly, some in the industry have long had concerns about the increasingly gargantuan scale of these floating holiday resorts. Nautilus International, a maritime trade union, has stressed since the event that “Nautilus is by no means alone in voicing concern at underlying safety issues arising from the new generation of ‘mega-ships’ – whether they be passenger vessels carrying the equivalent of a small town or container-ships with more than 14,000 boxes on-board”.

However, despite proportions that would have made Archimedes jump out of his bathtub in disbelief, it’s not the physics of displacement that raises the biggest concerns about the safety of modern cruise ships. Speaking to the BBC, Philip Wilson, Professor of Ship Dynamics at the University of Southampton, assured potential cruisers that, physically at least, “modern ships are as safe as they can possibly be”, despite their increasing size. “Instinctively it doesn’t look right”, he agrees, “but it is in fact very, very stable. The centre of buoyancy is in the right place”.

That’s not to say that modern ships are unsinkable – obviously. “Every ship will sink if you make the hole big enough” confirms Professor Wilson. And when disaster strikes, it turns out that size does matter.

“Mega-ships” such as the Costa Concordia can carry over 4000 passengers and crew, and, according to Nautilus, “the sheer number of people on-board raises serious questions about evacuation”. Current safety guidelines from the International Maritime Organisation (IMO), the United Nations agency responsible for shipping, stipulate that after any incident “a passenger ship should remain viable for at least three hours, to allow for safe, orderly evacuation and abandonment”. But in the case of the Costa Concordia, which struck rocks at 21.42 on the Friday evening, over eight hours elapsed before evacuation was deemed complete at 04.46 the following morning. In the interim, the ship seriously listed, first in one direction and then in the other, before losing power and taking on water, with passenger footage paying testament to the on-board chaos that resulted.

In the realm of emergency evacuation, therefore, it seems we’ve made little progress since the days of the Titanic. But, why? Surely a modern society that has the scientific and technical knowledge to build giant particle accelerators and clone a variety of farmyard animals should be able to work out how best to empty a sinking ship?

All passenger ships built since 1999 are required to undergo an ‘evacuation analysis’ at an early stage of design in order to “identify and eliminate, as far as practicable, congestion which may develop during an abandonment”. However, such analyses are notoriously unreliable because of the range of factors impacting how people behave in such situations. Analyses of shipping accidents have demonstrated that crowd density, psychological factors such as mass panic and the distribution of natural leaders, and the listing and motion of a ship all have significant effects on evacuation time, and are difficult to accurately model. One catamaran that recorded an eight minute evacuation time during a drill took an additional 70 minutes to abandon during a real incident. While more sophisticated modelling techniques that take all of these factors into account are now being developed, they are only just beginning to be used in ship design, and the increasing size and density of cruise ships makes the evacuation environment an increasingly complex one.

So, maybe it’s time to downsize. After all, who wants to spend their precious time off with 4,000 other tourists?

Unfortunately for passengers, cruising is big business, and, for the cruise operators, cutting back on numbers just doesn’t make sense. “It’s a perilous business to make money in”, according to one industry analyst, and it’s easy to see why. For one thing, the cruising business has incredibly high fixed costs – costs that stay the same regardless of the number of passengers – making it essential to fill as many cabins as possible in order to break even. The more passengers a company can cram onto a ship, the higher the profit margins, and the more quickly they can pay back the cost of building the ship in the first place – €450m in the case of the Costa Concordia. For cruise operators, bigger is definitely better.

So, despite the tragedy of the Costa Concordia, it’s likely that monster ships are here to stay. And with mere mortals at the helm, it’s probably sensible to plan for the worst. Until cruise operators start doing so more effectively, it might be prudent to enjoy the smaller things in life instead.

Image: flickr | EU Humanitarian Aid and Civil Protection

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