This report presents the findings of research investigating the opportunities and barriers to promoting sustainability in New Zealand’s rail system. The research involved two main aspects: exploring what sustainability means in a New Zealand rail context; and, investigating what opportunities and barriers might exist to achieving a sustainable rail system. Opportunities and barriers were considered in terms of their likely timescale and whether they were internal (systemic) or external (non-systemic) to the rail system. The research is intended to stimulate discussion about the role of rail in New Zealand’s transport system in the future. As part of this ongoing discussion, this report concludes with a number of recommended actions that could be undertaken to promote sustainability in the rail system.