Reduced Vertical Separation Minima (RVSM) was implemented in 2001. The pre-implementation safety analysis of ACAS II performance in RVSM had been, by necessity, based on prediction of the RVSM operational environment. The ASARP project measured and analysed the actual safety performance of ACAS II in European RVSM airspace, using up-to-date operational data, and assessed whether the ACAS II safety benefits anticipated prior to the introduction of RVSM operations were indeed achieved. To do so, the study replaced the operational assumptions made prior to RVSM introduction by actual RVSM operational data.

ACAS, as observed in actual operations, provides substantial safety benefits in European RVSM airspace. These benefits are also significant in the case of RVSM multiple aircraft encounters even though the risk reduction is four times less significant in such circumstances.

The results of the study were presented at the 30/05/2006 Seminar.