Exxon Valdez oil spill a number of recommendations, such as changes to the work patterns of Exxon crew in order to address the causes of the accident. In response to the spill, the United States Congress passed the Oil Pollution Act of 1990 (OPA). The legislation included a clause that prohibits any vessel that, after March 22, 1989, has caused an oil spill of more than in any marine area, from operating in Prince William Sound. In April 1998, the company argued in a legal action against the Federal government that the ship should be allowed back into Alaskan waters. Exxon claimed OPA was
Oil tanker instrument, Shell consulted the "London Tanker Brokers’ Panel (LTBP)". At first, they divided the groups as "General Purpose" for tankers under ; "Medium Range" for ships between 25,000 and and "Large Range" for the then-enormous ships that were larger than . The ships became larger during the 1970s, which prompted rescaling. The system was developed for tax reasons as the tax authorities wanted evidence that the internal billing records were correct. Before the New York Mercantile Exchange started trading crude oil futures in 1983, it was difficult to determine the exact price of oil, which could change with every contract.