11 July 2017
Quantitative risk assessment techniques are changing the way in which amusement rides are designed, inspected and operated. Modern rides are becoming dependent on computer-based technology with control systems allowing rides to perform increasingly complex functions at very high speeds. Passenger safety can depend on the correct operation of control systems and their failure could compromise safety.
Such developments mean that quantitative risk assessments are increasingly being applied to amusement rides.1 A quantitative risk assessment involves calculating the magnitude of a potential loss and the probability that such loss will occur. An acceptable risk is only understood or tolerated where the cost or difficulty of implementing an effective countermeasure exceeds the expectation of loss.
The importance of quantitative risk assessment techniques was confirmed by a November 2016 study on the generic safety-integrity requirements of amusement rides. The study, which had input from a steering committee of industry representatives, illustrated the benefit of applying quantitative risk assessment techniques to the themed entertainment industry.
Whilst quantitative risk assessment techniques have become commonplace in other industries, they have been slow in moving to the themed entertainment industry. The new study illustrates how such techniques can be used to determine the target safety-integrity level for control systems of diverse types of rides with the intention of encouraging their use. Having determined the target safety-integrity level, a designer can then use appropriate techniques, such as multiple channels or extensive internal diagnostics, to ensure that the rate of potentially dangerous control system failures is sufficiently low.
Even in advance of being compulsory, quantitative risk assessment techniques are quickly becoming established as industry best practice which anyone involved in the design, inspection or operation of rides may be expected to have considered or followed. In the event of an accident, parties could be shown to be at fault if the designed control system fails to satisfy a target safety-integrity level. Where quantitative risk assessment techniques have not been considered, parties might be required to justify why that was considered appropriate.
In terms of what these developments mean for those in the industry and the practical steps that can be taken the position is as follows:
- Ride designers: Whilst there are a number of industry standards that provide guidance on ride design, they generally only cover the physical requirements of rides. In contrast, guidance relating to control systems has been sparse, which is clearly inadequate given their increasingly important role. The November 2016 guidance should therefore be welcomed by ride designers as it provides clarity as to how to approach design in an area where little information was previously available. Quantitative risk assessment techniques should be considered as part of a ride’s design with target safety-integrity levels being identified for new ride orders. To achieve a high safety-integrity level, designers should incorporate appropriate diagnostic functions. This in turn is likely to lead to a review of the quality of operation and maintenance manuals. Ride designers should ensure that adequate documentation is provided that fully describes the requirements for commissioning, maintenance and operation of a ride, particularly for those safety functions that may lie dormant until a fault arises.
- Ride inspectors: The November 2016 guidance should also be welcomed by ride inspectors, who are often required to examine and certify rides with complex control systems for which little information is available. This can lead to inspections being either difficult to carry out or at worst inadequate. The new guidance provides much needed clarity for inspections. The safety functions of a ride should be thoroughly inspected to maintain the required safety-integrity level. In view of a ride’s hidden safety functions, this will continue to require checks against the safety documentation issued by the ride designer, confirming the importance of that information.
- Operators: End users should ensure that quantitative risk assessment techniques have been considered as part of a ride’s design and that safety-integrity levels are fully understood. Such information will impact on a ride’s commissioning, maintenance and operation stages. The higher the safety-integrity level, the higher the quality of the maintenance that will be required. Instructions within the operation and maintenance manual should also be carefully followed, with operators ensuring that adequate systems and training are in place to achieve compliance. Scopes of services in new ride contracts and in appointments for ride inspectors should also be reviewed and refreshed to ensure such principles have been adequately covered as part of the design and inspection process. Where they are not to be considered, parties should retain a record of the risk assessment which led to the conclusion that they could be dispensed with.
1 A study of the generic safety-integrity requirements of fairground rides, A M Wray, Health and Safety Executive (RR1080 Research Paper), November 2016