Sociotechnical systems are those which rely not only on technology but on humans and social organisation for their adequate functioning. The analysis of sociotechnical systems poses the particular challenge of synthesising methods appropriate to formerly separate scientific disciplines. One result is that prominent features of the systems are often missed during analysis. This paper points to some features of the ACAS/TCAS transport aircraft collision avoidance system which I believe could do with much closer scrutiny. 1 The
Peter B. Ladkin