|Authors:||Knut Veisten, Rune Elvik, Paal Brevik Wangsness|
|ISBN (digital version):||978-82-480-1735-6|
The report presents a cost-benefit analysis of a measure of extending the runway end safety area at the southern end of Tromsø Airport Langnes. The purpose of the measure is to reduce the potential impact if an airplane overrun the end of the runway, in a landing or a take-off in direction towards the south. The starting point of the analysis is to use a location probability model for overrun events (and undershooting), applying the reported parameters from a Weibull survival function of locations in longitudinal and lateral distance from the runway end and the centre line. This yielded an estimate of the relative frequency of locations in what is currently "missing outer rectangles" in a (too narrow) runway end safety area at Tromsø Airport. About 10-15% of airplanes overrunning or undershooting are likely to be affected by the narrowed runway end safety area. As there are edges on each side where the airplane might fall down (the narrowed area is due to a road tunnel passing under), the expected damage in case of an overrun will be higher at Tromsø Airport compared to other Norwegian airports, everything else equal. The consequences comprise damage to the aircraft, installations and passengers, as well as subsequent delays or close-downs. The estimated distribution of damage, for different levels of accidents and incidents, with associated damage costs, was primarily based on international literature. The estimated benefit-cost ratio was just below one. The input data are uncertain. Applying simulations, drawing from a set of input value intervals, 90% of the simulated benefit-cost ratios end up within the interval from 0.6 to 1.3, with an average of about 0.92. Possible alterations of the estimated cost of the measure are most decisive for the result of the cost-benefit analysis.