Since its opening in 1867, the Christchurch to Lyttelton line had become extremely busy with both suburban and goods trains passing through the Lyttelton Tunnel, which had been opened in 1867. Smoke accumulating in the tunnel from each successive train became a nuisance for train crews and passengers travelling through the tunnel. Although trials were conducted in 1909 using steam locomotive WF 436 which had been converted to oil firing, the cost of oil alone meant that no further work was done.