Responding to risk of safety critical infrastructures through a systems thinking approach:The case study of road tunnels

Abstract

Η παρούσα διδακτορική διατριβή εξετάζει το θέμα της διαχείρισης κνδύνων οδικών σηράγγων υπό το πρίσμα της συστημικής μεθοδολογίας.

Over the last two decades there has been a great increase in the number of road tunnels worldwide. However, the increasing number of these infrastructures is a double-edged sword also raising upfront an endogenous problem, which is the severity of accidents that may occur. To cope with this problem, the European Commission launched the Directive 2004/54/EC that sets minimum safety requirements and suggests the implementation of a risk assessment in several cases. However, the EU Directive does not indicate either the method for performing the risk assessment or the criteria for risk acceptance. Therefore, a wide range of methods have been proposed most of them based on Quantitative Risk Assessment (QRA). Although QRA contribution to manage safety has been important in many fields, it has been argued that QRA results should not form the sole basis for safety-related decision making since QRAs have limitations to consider: (1) the treatment of human performance, including not only human error per se but also management and organizational factors, (2) the kinds of failure modes that may be introduced by software, and (3) the adaptation of the system over time. Taking into account that road tunnels are not merely technical, engineering systems but also have intrinsic organizational, social and managerial dimensions that impact or contribute to their safety, the objective of this thesis is to propose an innovative method that has the ability to provide decision-makers with scenarios that even if they have not been considered by traditional road tunnel QRAs they have the potential to lead to safety issues. In order to achieve the objective, a change in the accident modelling paradigm seems to be essential. The hypothesis made in this thesis is that systems theory provides the foundation to create a road tunnel safety assessment method that has the ability to capture the “residual” risk which is left unnoticed by current road tunnel QRAs and provide guidance for responding to it. The systems-theoretic method introduced in this thesis is primary based on the STAMP accident model. However, in order to give the opportunity to the safety analysts to search deeper for organizational pathologies and vulnerabilities, an extension of STAMP has been made with concepts from an organizational model, i.e. the Viable System Model (VSM). The joint STAMP-VSM framework is incorporated into the systems-theoretic road tunnel safety assessment method and is evaluated through an illustrative case study. The results revealed that the proposed method succeeded in copying with the several aspects that are not adequately handled by current road tunnel QRAs.