engine room is quickly flooded, leaving the ship without propulsion. If two holds in the middle of the ship are flooded, the stress on the hull can become so great that the ship snaps in two. Other contributing factors were identified: Most shipwrecks involved ships over 20 years in age. A glut of ships of this age occurred in the 1980s, caused by an overestimate of the growth of international trade. Rather than replace them prematurely, shipping companies were compelled on cost grounds to keep their aging vessels in service. Corrosion, due to a lack of maintenance, affected the seals of the hatch covers and the strength of the bulkheads which separate holds. The corrosion is difficult to detect due to the immense size of the surfaces involved. Advanced methods of loading were not foreseen when the ships were designed. While the new processes are more efficient, loading is more difficult to control (it can take over an hour just to halt the operation), occasionally resulting in overloading the ship. These unexpected shocks, over time, can damage the hull's structural integrity. Recent use of high-tensile steel allows building a structure with less material and weight while retaining similar strength. However, because it is thinner than regular steel, HT steel can corrode more easily, plus it can develop metal fatigue in choppy seas. According to Lloyd's Register, a principal cause of sinkings was the attitude of ship-owners, who sent ships with known problems to sea. The new rules adopted in the 1997 annexes to the SOLAS convention focused on problems such as reinforcing bulkheads and the longitudinal frame, more stringent inspections (with a particular focus on corrosion) and routine in-port inspections. The 1997 additions also required bulk carriers with restrictions (for instance, forbidden from carrying certain types of cargoes) to mark their hulls with large, easy-to-see triangles. Crew safety Since December 2004, Panamax and Capesize bulk carriers have been required to carry free-fall lifeboats located on the stern, behind the deckhouse. This arrangement allows the crew to abandon ship quickly in case of a catastrophic emergency. One argument against the use of free-fall lifeboats is that the evacuees require "some degree of physical mobility, even fitness" to enter and launch the boat. Also, injuries have occurred during launches, for example, in the case of incorrectly secured safety belts. In December 2002, Chapter XII of the SOLAS convention was amended to require