 Following major train disruptions on 15 and 17 December 2011 , the Committee of Inquiry ( COI ) found that despite the first refurbishment of the C151 rolling stock , " there does not appear to be any upgrade in terms of engineering components " . The COI was particularly critical of the inadequate and ageing emergency battery installed on the C151 and recommended the installation of a Train Integrated Management System ( <unk> ) found on the C751B and C151A trains . 
