82 Book Reviews / Safeq Science 21 (1995) 79-84

papers written by engineers and others state as though it is a fact that people do, as though it is an obvious fact which is without challenge. Such contradictory statements or positions found in the book are a little unfortunate. It might have been possible to overcome this problem. The editors, for instance, could have played a role in highlighting the contradictions and errors, orthe authors themselves could have been given the opportunity to revise their papers in the light of the information they gathered at the conference on which the book is based.

Overall, the book has many individually worthwhile papers which will be of interest to a wide variety of professions. It is to be hoped in this context that readers will not confine themselves to the contributions that are from within their own discipline. What the book does not provide, however, is a coherent and integrated whole. Responsibility for that lies with the editors rather than the authors.

lan Donald

A Guide to Practical Human Reliability Assessment, by Barry Kirwan. Taylor and Francis, London, 1994, 580 pp.

This new textbook represents a significant contribution to the published literature on Human Reliability Assessment. Kirwan has deliberately set out to present a "state of the art" review of the Human Reliability Assessment (HURA) process and the available methods for Human Error Identification (HEI) and Human Reliability Quantification (HRQ). Drawing heavily upon previous papers and reports and upon his own experiences as a human reliability practitioner, researcher and consultant, the book contains a thorough review of currently available methods for HRA. A student or a practitioner would find this a useful reference source. The book contains no new theoretical ideas and indeed claims only to focus on the practical issues of HRA by presenting a"toolkit" of available methods.

Human Reliability Assessment is a method for assessing the risks attributable to human error and reducing a system's vulnerability to the effects of those errors. Kirwan outlines the HRA process as it is usually carried out and integrated into a PSA/QRA assessment. He assumes the driver for using human reliability techniques will be such an assessment. No mention is made of other potential drivers and, in particular, it is disappointing that these is no reference to human reliability issues in Safety Cases. The focus of the book is on the nuclear and chemical sectors with some reference to offshore assessments. The issue of how the HRA process and methods can be kused in okther industrial sectors is only covered in a cursory manner. Availability of data and resources and the driven for using HRA is other industrial sectors are important aspects.

The book contains a detailed review of Human Error Identification (HEI) methods. These are methods for identifying what kinds of human failures can occur. This section considers methods for identifying mainly unintentional human errors at the skill and rule based level of performance. Problems with identifying so-called "cognitive errors" are addressed. Recent advances in methods of assessing violations receive little coverage.

The key section of this book and the one which will probably be read most widely is the review of Human Reliability Quantification (HRQ) methods. HRQ methods aim to provide

Book Reviews/Safety Science 21 (1995) 79-84 83

an assessment of how likely human errors are. This book contains a comprehensive and up to date review of established HRQ methods. There is perhaps rather too much focus on methods that Kirwan has developed himself although these have not been described in such detail in a widely available text before. Issues such as the availability of data, the validation of methods, and the resources required to use the HRQ methods are all covered in this section together with useful examples of each of the techniques. Indeed another positive feature of this textbook is the significant number of illustrative case studies of the HEI and HRQ methods which are given.

Error reduction was a short section of the book rather limited in scope. To some extenf this was compensated for by the appendix containing a human factors checklist but it was disappointing that this important aspect of Human reliability was not treated in more depth.

Recent accidents such as the Kings Cross underground fire, the Clapham lunction train crash and the sinking of the "Herald of Free Enterprise" Ro-Ro ferry at Zeebrugge have all emphasized the importance of management and organisational factors in the prevention of accidents and major disasters. Kirwan recognises this trend but the section of the book looking at management and organisational aspects is limited. Indeed he explicit excludes such factors as being currently outside the remit of the HRA process. It is hoped that this situation will change in the very near future and that the number of available method for such assessments will increase.

Given the focus of the book on the HRA process I would have anticipated consideration of implementation issues such as planning for HRA, building up a capability in-house to carry out such assessments, the criteria for selecting external help, and so on. Above all, some indication of the level of resources which would normally be required for a typical HRA assessment would be very useful for the practitioner starting out on the process for the first time. Perhaps these issues could be added if the book were to be reprinted as a second edition. If so, it would be helpful if the reference lists and some of the examples were checked for mistakes since a fair number were spotted by this reviewer. Overall this is a worthwhile addition to the liberary of any organisation currently using or considering the use of HRA techniques. It is complementary to recent theoretical studies of human error and human reliability and should be read in conjunction with warnings about the limitations of the current HRA process which these texts contain.

iii

Deborah Lucas AEA Technology ( Consultancy Services)

Target Risk, by G.J.S. Wilde. PDE Publications and Castor & Columba, Toronto, 1994, 234 pp.

People engage in risky behaviour because it has net rewarding consequences. At any point in time, those rewarding consequences determine the amount of risk a person is prepared to tolerate. Whence the concept of 'target risk', its elaboration in Risk Homeostasis Theory and the conclusion that safety interventions that do not reduce 'target risk' (i.e. the net reward for risk-taking) are ultimately doomed to failure.