In response to the Exxon Valdez incident, the Oil Pollution Act of 1990 was enacted as allegedly comprehensive oil pollution legislation. The Act enforces double-hull requirements for tank vessels in U.S. waters, except designated lightering zones or deepwater offshore oil ports, until 2015. The requirements are efficient in preventing oil spills but suffer from cost ineffectiveness because of the large expenditures associated with them. In response to the increase in capital and operating costs, the shipping industry has changed its operation patterns to take advantage of cost-efficient older single-hull tankers in U.S. waters. In particular, the retirement deadlines of single-hull vessels under the Act have had the paradoxical effect of encouraging tanker owners to "milk" their vessels up to the end of their legal economic lives. The Act has led to an unexpected and undesirable situation in controlling oil pollution risks, which calls for taking appropriate measures to ensure the adequate operation of the older single-hull vessels.