The emergence of poor air quality as a major urban transport problem is considered through the case of Oxford (UK). The relevance of the Oxford policy approach for air quality management is appraised. The level of oxides of nitrogen emitted from large diesel-powered vehicles, most notably buses, emerges as a particular public health problem; the Achilles' heel of a successful record in promoting public transport use and traffic restraint. It is concluded that similar problems may affect bus-centred transport strategies in other urban areas, and that a change of bus technology is the necessary mitigation measure. The findings confirm the importance of ensuring that sustainable transport strategies are fully holistic and integrated in their policy goals and outcomes. © 2004 Published by Elsevier Ltd.