An in-depth on-scene study of forty-two road tanker incidents with flammable loads was conducted in New South Wales over a period of fifteen months by teams each consisting of an Engineer and a Behavioural Scientist. The report describes notification arrangements, site attendance and investigation techniques used in the study. Results include a listing of all the factors encountered. These are generally classified as mechanical, environmental and behavioural factors. Special mention is made of the potential for improvements in tanker stability, tanker design and tanker maintenance. An Appendix includes all the case histories.