Assessing crowd safety risks : a research into the application of the risk assessment principles to improve crowd safety management and planning in major public venues
This thesis considers the subject of crowd safety and investigates how the application of risk assessment can provide support for decision making in crowd safety management and planning. The focus is on major public venues and events where large crowds arc a normal part of the operation. Conventional methods of assessment tend to be ad hoc, reactive and rely on individual experiences. The risk assessment approach, which is comprehensive, systematic and pro-active, can help to overcome these shortfalls. Risk assessments have already been successfully applied in many workplaces, ranging from high hazard industrial plants to the office environment. However, this thesis argues that for it to be of benefit, the risk assessment must be appropriate to the nature of the operation and the nature and the extent of the hazards involved. The existing risk assessments are inappropriate to crowd safety in this respect and a more suitable methodology is required. In order to identify the methods and tools that could provide the potential solutions to the problems of assessing crowd and behaviour related hazards, a review of other risk assessments was conducted. It has highlighted a number of techniques and tools that could be applied to assess crowd safety risks. Based on the criteria mentioned above and the findings of this review, a prototype crowd safety risk assessment methodology was developed. A series of trials were conducted to evaluate the validity and usability of the prototype. Revisions were made accordingly to produce the final draft. Experiments and a questionnaire survey were then carried out on the final draft to test and verify the methodology. In general, they show that the methodology has led to an improvement in most aspects of crowd safety risk assessment. In the experiments that compared the methodology against methods representing the existing risk assessments and the conventional way of assessing crowd safety, subjects using the methodology tend to perform better in most areas. More hazards were identified. In the evaluation of risks, better consistency was achieved between individuals using the methodology. However, their judgements appeared to be less consistent over time. The use of a larger rating scheme with more choices available in the methodology could have an impact on consistency in risk evaluation. Another key factor could be that the subjects who took part in the experiments were all novice assessors. Possible learning effect may have occurred in between experiments, which could have resulted in a change of mind over time. If this is the case, this result could be an indication that the methodology is more sensitive to changes in risks or risk perception. It will be interesting to find out if experienced assessors can achieve better consistency. By and large, the experiments and questionnaire survey have served to verify, at least in part, the arguments that risk assessment is better than the conventional assessment method and that there are more benefits to be gained when the risk assessment is more appropriate to the nature and the extent of the crowd safety hazards that could arise in major public venues. Nevertheless, it is important to recognise that the research work presented in this thesis is merely the first step towards a crowd safety risk assessment methodology. There are outstanding issues yet to be resolved, not least the issue of the apparent lack of consistency over time in risk evaluation. This thesis has identified the research and development work that is required to resolve these issues and to further the benefits that risk assessment could bring to crowd safety.