John May's  research group the Safety Systems Research Centre, is a part of the South West Nuclear Research and Teaching Hub, in which he is an operational board member, and lead for research theme 'Reliability, resilience and security'. The SSRC studies risk in a new breed of highly complex systems built by man. Existing scientific and engineering techniques have been unable to describe or control these phenomena.

For example, it was previously thought to be the case that non-trivial software based systems were untestable, in the sense that testing could not provide meaningful quantitative assurance of software reliability. We have demonstrated that this not the case for a significant class of software, and have applied new statistical reliability testing techniques to critical nuclear systems, including reactor protection systems and smart devices. The latest research, conducted with UK nuclear licensees and ONR (regulator), in the CINIF programme, is enhancing the power of these techniques to demonstrate higher reliabilities and apply to a wider class of systems. 

Socio-technical systems also exhibit complex systematic failure behaviour, the result of which can be seen in repeated large industry accidents (Fukushima, Boeing, Macondo, Chernobyl, Bunsfield, Hatfield, Piper Alpha, etc.) SSRC is developing new ideas for the control of dangerous accident precursors in large organisations.

Last but certainly not least, the research group is developing a new method to evaluate risk, based on the 'J-value'. This can be used to prioritise mitigation activities and understand where best to allocate the costs of protecting against disasters.