The determination of safe separation of aircraft taxiway is the focus of airport graphic design. This paper proposes a method to determine safe separation from the perspective of assessing the risk of aircraft taxiing deviation. By analyzing the deviation distribution characteristics of aircraft taxiing, applying the test data of taxiway deviation provided in relevant reports, the threshold is determined based on extreme value theory and generalized Pareto distribution(GPD), and on the basis of sorting out the influencing factors of taxiway deviation, the deviation probability model of taxiway is established by means of logistic regression and least square method. Finally, taking the taxiway to fixed object separation of Chicago O'Hare International Airport as an example, the risk matrix and the model are used to evaluate the risk, and the more secure separation and the restrict conditions of taxiing are put forward, thus providing a theoretical basis for the determination of the safe taxiway to fixed object separation.

CICTP