Maritime accidents increased according to the square of the increase in traffic by the middle of the 19th century in the UK. The act granted strong power of inspection to the Board of Trade and introduced the Plimsoll line, which was intended to decrease accidents caused by overloading. In 1912, the loss of the TITANIC, regarded as an unsinkable ship, was significant both in scale of an accident and investigations that followed and were recorded and issued officially, both in the UK and in the United States. The extensive accident investigation found hardware issues, human errors and organizational issues. In marine accident investigations, the focus of transition has been partly influenced by accident investigations in aviation and nuclear power plant industries, and the development of human factors and accident models. During 1970s to 1990s, when those major organizational accidents had been occurring across the fields, there were important developments in human factors and accident models.