From the 1970s St Blazey was mainly used by diesel locomotives hauling freight trains, and many of these only operated during the week so that at weekends half a dozen main-line locomotives could be at the depot awaiting active duty. However one passenger train in the late 1970s was booked for haulage by locomotives normally operating from St Blazey, this being the summer Saturday service between Newquay and Newcastle with a pair of Class 25s operating to Plymouth, but by 1980 this had ceased. Class 37s operating from St Blazey were never booked on passenger turns.