The DA class were employed on all the major lines in the North Island: the NIMT, Marton-New Plymouth, Palmerston North-Gisborne and North Auckland lines. The success of the DA class in its reliability and performance meant that it was the major factor allowing the withdrawal of North Island steam locomotives by 1967. The class were successful in raising the freight capacity of the NIMT. The main limitation was the Raurimu Spiral, where a pair of DA class locomotives could haul 650 tonnes up the grade compared to 595 tonnes for their KA class steam predecessors.