(17)Regulation 20 of Annex I to MARPOL 73/78 introduces a requirement that all single-hull oil tankers may only continue to operate subject to compliance with a Condition Assessment Scheme (CAS), adopted on 27 April 2001 by Resolution MEPC 94(46) as amended by Resolution MEPC 99(48) of 11 October 2002 and by Resolution MEPC 112(50) of 4 December 2003. The CAS imposes an obligation that the flag State administration issues a Statement of Compliance and is involved in the CAS survey procedures. The CAS is designed to detect structural weaknesses in ageing oil tankers and should apply to all oil tankers above the age of 15 years.