 Although the Kirkdale is the largest depot, most heavy maintenance is carried out at Birkenhead North TMD.Units transfer between the two depots by travelling into platform 2 of , changing ends, then taking the single track, bi-directional stock transfer line to platform 2 at , before continuing towards Birkenhead.Operation of Kirkdale depot was transferred from Merseyrail to Stadler Rail Service UK in October 2017.