There has been a lot of mirth about the US Coast Guard regulation requiring passenger vessels to alter stability calculations in relation to the "Assumed Average Weight Per Person".
Effective 1 December 2011, the Assumed Average Weight Per Person was increased from 160 lbs. to 185 lbs. The impact on US flagged passenger vessels is significant, particularly smaller types. In Washington State the ferry system declared that (rather than weigh every passenger) they would be reducing their passenger capacity to stay within the stability criteria established for each ship. (I'm not sure about the heeling moment that would occur in a ship like the Puyallup if everyone ran to one side).
It's not just Americans
In fact, during the notification phase the USCG received several submissions. At least two recommended that the AAWPP be increased to 187 lbs., the actual average weight of American adults.
Before anyone starts pointing too quickly at the population of the US there should be some heed paid to decisions by the International Maritime Organization's Maritime Safety Committee. The MSC made amendments to the International Life Saving Appliances code taking effect in October 2010 and then again to take effect 1 January 2012.
Under international rules the former average assumed weight of occupants of lifeboats, liferafts and rescue boats was 75 kg (165 lbs). Effective Oct 2010 the new assumed average weight of all persons, worldwide, getting into a lifeboat became 82.5 kg (182 lbs). As of 1 January 2012 the new mass of 82.5 kg per person applies to all survival craft, worldwide.
Looks like we're all getting fatter.
Good question: From Christina, in comments, about life jackets and whether there have been any changes to match the changes in survival craft. The answer is, YES. Go here for details.
Update 30/12: The infant lifejacket requirement noted above prompted an offline question: How many?New requirements for the carriage of additional equipment, also effective July 1, 2010,
have been introduced under the SOLAS Convention, as follows:
• On all ships where adult lifejackets are not designed to fit persons weighing up to 140 kg with a chest girth of up to 1,750 mm, suitable accessories are to be provided that allow the lifejacket to be secured to such persons.• All passenger ships are to be provided with lifejackets for “infants”.
The answer is as follows:
1. For vessels on voyages under 24 hours: 2.5 percent of the total passengers.
2. For vessels on voyages of 24 hours or greater: An approved "infant" lifejacket for every infant onboard.
Infant lifejackets should be marked INFANT.