(15)Important amendments to Regulation 20 of Annex I to MARPOL 73/78 were adopted on 27 April 2001 by the 46th session of the MEPC by Resolution MEPC 95(46) and on 4 December 2003 by Resolution MEPC 111(50) in which a new accelerated phasing-out scheme for single-hull oil tankers was introduced. The respective final dates by which oil tankers must comply with Regulation 19 of Annex I to MARPOL 73/78 depend on the size and age of the ship. Oil tankers in that scheme are therefore divided into three categories according to their tonnage, construction and age. All these categories, including the lowest one, Category 3, are important for trade within the Union.