 From 1941 the "Spirit" was occasionally hauled by VR's H class 4-8-4 locomotive in the event of one of the S class locomotives not being available.Although the H class was limited to a maximum 60 mph (96 km/h) top speed, its superior performance climbing steep gradients along the route reportedly compensated for its reduced top speed enabling it to maintain the timetable.From 1952 deliveries of B class diesel locomotives commenced and the new locomotives quickly proved their superiority to steam traction in availability, reliability, and cost-effectiveness of operation.