This paper describes a new measure of the sustainability performance of public transport in 88 world cities adopting 15 indicators including Environmental, Social, Economic and System Effectiveness sustainability. Sustainability performance is then explored for cities with only "Public" operations or others with some degree of commercial operation ("Non-Public")Results show no significant difference in aggregate total sustainability indicator scores between world cities with "Public"/"Non-Public" operations. However Social Sustainability indicators are significantly different with "Public" operations having better Social Sustainability performance than "Non-Public".For individual component indicators, three of the four Social Sustainability component indicators have average normalised scores suggesting statistically significant differences between "Public" and "Non-Public" city scores with "Public" cities performing better than "NonPublic". The indicators and their relative advantage to "Public" cities being Trip distance (24%), Affordability (34%) and PT related deaths (29%). However results also show that operating costs per passenger km and cost recovery are higher in "Non-Public" cities suggesting higher elements of Economic Sustainability in "Non-Public" based Public Transport citiesThe paper concludes with a summary and discussion of the results including implications for regulatory practices and areas for future research.[186 word Max=200]