Earlier papers, based on a computer model of European air traffic, deal with the probability of conflicts arising between pairs of aircraft operating under free-flight rules. This paper discusses the problems of resolving these conflicts. When a potential collision takes place in the neighbourhood of other intruding aircraft, these must be taken into account when choosing an escape manoeuvre. A suggestion is made that may ease the problem.

This paper presents a concept on the subjective ship domain. The factors related to the domain are discussed. A method based on the neural networks is used to establish a model of the domain that considers the effects of visibility and manoeuvrability, which can react quickly to various ships within a certain range.

Loran-C receivers measure time delay differences in the signals they receive, compute differences of distance, and hence determine the user's position. The conversion from time to distance requires knowledge of the signals' velocities, which differ when propagating over sea or land. Precise positioning requires the delays of land paths to be accurately mapped, a procedure traditionally entailing expensive and time-consuming marine surveys. The resulting data, in the form of Additional Secondary Factors (ASFs), may be stored in Loran receivers. This paper introduces the concept of Loran-C Additional Secondary Factors, and shows how it is possible to map them efficiently. It focuses on recent advances, chiefly the development of powerful software for modelling the growth of ASFs over mountainous terrain. This employs an implementation of an algorithm proposed by Monteath. The modelling capability of the algorithm is demonstrated by examining propagation along a route that crosses mountains and deep fjords. In addition, the ASFs it predicts are compared with sample measurements made around the west coast of Scotland.

In an earlier study, the author attempted to give some quantitative estimates of the problems that free flow might face in Europe. The study was based on a traffic sample from the Eurocontrol Route Charges Office for a busy day in 1991. More recently, they generously made available a similar sample for a day in 1997. Using this new data, the study has been extended to cover wider aspects of the free flow problem. The central problem is that of ensuring safety. This will require a mechanism to detect collision threats and safely to resolve the problems. Possible tools are ground-based surveillance and/or airborne systems. This paper will use computer modelling to predict the loads that these detection and resolution systems must face.