The Impact of Reduced Vertical Separation Minima (RVSM) on Air Traffic Safety Occurrences in the UK Airspace Using Intervention Models

Maintaining high levels of safety is essential within the air transport industry because aviation accidents are considered to be low probability but high consequence events. In order to prevent repeat occurrences of the same type of accident, it is important to have an understanding of why they occur and of any underlying trends in contributory factors. Research suggests that occasionally, the implementation of new technologies and procedures within air traffic management can result in unforeseen, negative safety issues. The rising demand for air travel is driving the need to increase global aviation capacity, and this brought about the introduction of Reduced Vertical Separation Minima (RVSM) in 2002 within the United Kingdom airspace. There were concerns that its introduction might affect safety levels, however since its implementation there has been virtually no scientific research conducted to evaluate its impact. This research aims to analyse whether aviation safety has been affected by the introduction of RVSM, whilst also understanding the impact that air traffic levels and seasonality might have on future safety levels. This paper uses airprox as a key safety performance indicator. Historical airprox (1999 – 2011) data were obtained from the UK Airprox Board and air travel demand data for the same period were gathered from the Civil Aviation Authority (CAA). An intervention model based on the seasonal autoregressive integrated moving average (SARMA) time-series method was applied to understand the relationship between airprox and air traffic levels, seasonality and the introduction of RVSM. The analysis confirms a strong relationship between air traffic levels and airprox, whilst also discovering that RVSM has a statistically significant relationship with safety levels. The findings are discussed along with an identification of limitations and areas for potential future research.