Since the full introduction of Automatic train operation (ATO) on the East Rail system in 2002, the rate of change of acceleration and deceleration resulting from ATO driving added stress to the underframe components. To allow a root cause investigation to be carried out, the use of the ATO system was suspended on 15 January 2006, leaving the operation of trains back in the hands of the train drivers, the safety of train operation under the control of the Automatic Train Protection system. This resulted in a decreased frequency (from 24 to 23 trains per hour) and lengthened trip time (increase by 90 seconds to 42.5 minutes). KCRC also temporarily transferred some staff from West Rail to cope with recent maintenance of trains.