Each Autumn a fleet of rail head treatment trains (RHTTs) operate in the UK to help keep lines clear of fallen leaves (leaf mulch) which can affect adhesion and cause wheel damage. The method used is to spray a jet of water at very high pressure onto the railhead, which washes away any accumulated leaf mulch. The trains - which are normally 'top and tailed' with two locomotives, quickly accumulate a thick coating of dirt, giving them an almost ghostly look at night. One of these trains is seen at Cardiff Central during a crew change. In the background a Great Western Railway HST arrives with the 08:45 London Paddington - Swansea service.