Keywords: system reliability, software reliability, human factors, IEC 61508, formal methods, fall-back options, storm surge barriers, The Netherlands, reliability assessment, critical infrastructures
Human factors in system reliability: lessons learnt from the Maeslant storm surge barrier in The Netherlands
The Maeslant storm surge barrier in the Netherlands is an interesting case in system reliability, first because of the great effort that has been put into making its operation reliable and into assessing its reliability, and second, because it has characteristics that make reliability assessment extremely hard. From its history a number of interesting conclusions can be drawn, of which the most important one is that there is no straightforward, definitive solution to reliability, but reliability is obtained and maintained in a continuous process of improvement. Other conclusions are that humans cannot be excluded from the operation or decision-making in systems such as the Maeslant barrier, that all methods for improving system reliability are most effective when the people involved are sharply aware of each method's limitations and that a continuous, open process of consulting a variety of experts is crucial to obtain the best possible reliability.