Category 2 tankers were used for a number of years and were planned to be phased out by 2010 at the latest, depending on the year of delivery. With MARPOL tankers, it is not allowed to use ballast tanks as cargo tanks. This has reduced operational spillage drastically. The downside is designs based on MARPOL spill more oil when damaged than a preMARPOL tankers. This is due to several factors:
