Comparison of Computation of Horizontal Overlap Probability in Aircraft's Collision Risk Estimation on Crossing Routes

This paper treats the horizontal overlap probability which is a key parameter of vertical collision risk formula. Main purpose of this paper is to compare two computation methods of horizontal overlap probability, both of which were proposed by EUROCONTROL. It is shown that the value of horizontal overlap probability evaluated by one computation is always smaller than or equal to the value evaluated by the other method. We also evaluate horizontal overlap probability by these methods numerically and conclude that the simpler approximation computation should not be used for the vertical risk estimation of crowded routes.