Generally the DXC sub-class is assigned to the South Island, as the modified air intakes were designed to assist in are useful for working the Midland Line, coal trains (see above) particularly in the formerly electrified Otira Tunnel section, whereas the DXB sub-class were predominantly assigned to the North Island. Following the introduction of the first twenty DL class locomotives, four DXBs were reassigned to the South Island for general freight service on the Main South Line, while DXC class locomotives have appeared in the North Island while on shakedown runs after overhaul.