Before the base tunnel opened, freight trains were shorter and invariably double headed. A sizeable fleet of SS1 electrics assisted the SS3s and SS3Bs to move traffic over Wushaoling summit. SS1s do still appear on freights between Lanzhou and Wuweinan but in much smaller numbers. Only seven different members of the class were identified over five days on the line. An unidentified SS1 led an SS3 on a northbound train of oil tanks between Longgou and Liujiatai on 22 September 2006.