(01 Nov 2018, 11:07 am)stagecoachfan wrote 22514 on driver training duties yesterday morning (displaying "Driver Under Instruction" "L"), but on the 13 by the afternoon (alongside 22515 on 13A)

More than likely was being used for route learning combined with type familiarisation before working 13/13A (all 6 vehicles work both routes - 3 work 13s from Salters Lane and 13A from Coulby with the other 3 working 13s from Coulby and 13As from Salters Lane).