“Visual meteorological conditions” (v.m.c.) specifies a forward visibility of at least, say, 5 miles, horizontal distance from cloud of at least, say, 2000 ft., and vertical distance from cloud of at least, say, 500 ft. At any instant, therefore, the airspace may comprise (a) v.m.c. areas (or strictly speaking volumes), and (b) non-v.m.c. areas. The dividing lines (or strictly speaking surfaces) between them may be perceptible or their positions predictable by the aircrew or they may not. If they are neither perceptible nor predictable, then the aircrew cannot possibly ensure that their aircraft does not enter any non-v.m.c. area and it cannot possibly ensure compliance with instructions to ‘maintain v.m.c.’. Whether the aircraft is in a v.m.c. area or in a non-v.m.c. area may be perceptible by the aircrew or it may not. If it is perceptible and if the aircraft immediately reverses direction in a small space, then the aircrew will almost but not quite be able to ‘maintain v.m.c.’. In some cases very small infractions of non-v.m.c. areas may be permissible; in others, not.

Traffic capacity is the capability of a waterway to deal with the traffic and when the traffic volume exceeds this limit traffic flow stops, as is often experienced on congested roads.

According to the U.S. Government Highway Capacity Manual the capacity of a highway with four or more lanes and free from conditions hindering smooth traffic flow has a maximum value of V/Ymin per lane, where V is the speed of a group of vehicles and Ymin is the average minimum separation of cars. Since Ymin is a function of V and increases rapidly and continuously with speed, there is a maximum value for V/Ymin which is a function of the speed. This is called basic capacity. Several examples of capacity together with the speeds of the transportation facilities are given in Table I.

The main concern of this paper is with the limitations of techniques already commonly applied, and in the more promising points of application for new technology in navigation, surveillance and traffic control. In seeking the latter, some of the current trends in other fields, particularly aircraft design, are taken into account. Considerable emphasis is placed on the efficient use of land at airports, in view of the strength of feelings aroused in ‘the community’ by the questions of apportionment and exploitation of land resources.

The recent collisions in the English Channel and the Dover Strait have caused a great deal of public disquiet in this country and the United Kingdom's Department of Trade and Industry's Safety of Navigation Committee were invited to discuss what, if any, measures should be recommended to Imco to improve the routing system in the Strait. The Institute of Navigation, with its French and German counterparts, was largely responsible for the introduction of the routing scheme in force in the Strait and has since its introduction in 1967, by means of a series of international working groups, kept a watchful eye on how things were going, and on occasions made recommendations for its improvement.

By the North European Trade Axis is meant the trade route from Ushant and Land's End, up the English Channel, through the Dover Strait fanning out to serve eastern England, the north coast of continental Europe and leading to the Baltic Basin. Recent events in this area have left a feeling that some form of tightening of control is not only desirable, but is rapidly becoming imperative. There is a basic conflict between the two forms of shipping using the area: the local users who use the area more or less constantly, and the long-distance traders, usually much larger, which arrive in the area for a brief stay after a prolonged period at sea, which has usually been in good weather conditions. Frequently these latter ships have a very poor notion of the hornet's nest into which they are steaming when they arrive. The net result is all too often the same: the local users, with familiarity breeding contempt, wander about as they see fit, with scant regard for routing or the regulations; all too often the big ships arrive from sea with navigating staffs who are too confused, sometimes too ignorant—and sometimes too terrified—to do much more than blunder forward in a straight line hoping for the best. Quite obviously this is not a total picture, and there are large numbers of ships which navigate perfectly competently, but the minority of those which do not seem to be rising rapidly, and show every sign of continuing to increase.

The air traffic controller provides a service and can do so effectively only with the cooperation of his customers, namely the pilots of many different types of aircraft. For the purpose of this paper it is assumed that pilots do not wittingly take avoidable risks and are fully capable of finding their way from one place to another by the shortest available route. According to I.C.A.O., A.T.C. exists to provide ‘safety and expedition’, but, left to his own devices, the pilot can take care of his own ‘expedition’ so that the main function of A.T.C. is to provide a safety service. When A.T.C. has to regulate flights for safety reasons, however, it may have to ask a pilot to deviate from his chosen flight path. It then has to assume a measure of responsibility for expedition, but safety is still the prime consideration.

In the October Journal, p. 538 and Table I on p. 539, it is shown that the number of collisions per fog day (abbreviated below to c/fd) has fallen by some 20 per cent since routing was introduced in 1967. It is not legitimate to assume without further argument that this is a case of cause and effect.

With the introduction of larger and faster types of air transport it seems certain that the importance of all-weather take-off and landing for their safe and economic operation will increase during the coming decade. This paper suggests that a vital factor in this development will be the availability to the pilot of up-to-the-minute information on low level visibility and wind conditions applicable to the runway he is to use. The difficulties of obtaining and forecasting these microclimatic factors are discussed.

We now stand at the beginning of a new decade and one which promises to be as progressive and stimulating for civil air transport as any of its predecessors. Great advances were made during the 60's in establishing and steadily improving the performance of sub-sonic jets. Of equal importance was the enormous amount of preparatory work for the introduction of jumbo jets, air buses and supersonic transports during the 70's, and none was more important than the early stages in developing an all-weather landing system. It may be hoped that by the end of this decade a fully operational all-weather landing system will be available for use at all major airports in the world and there is no doubt that progress towards this goal will be vital to the success of the S.S.T.

As a serving ship-master I have made many voyages in an 18,000-ton deadweight tanker (and an occasional trip in 50,000 tons) through the Dover Strait to Continental and U.K. ports. I should like to supplement Commandant L. Oudet's article on the ‘Reversal of the Traffic Flow in the Dover Strait” with a few comments from my own experience.

In recent years attempts have been made to reduce the manpower requirements of merchant ships and, largely as a consequence of technological advances, some measure of success has been achieved. Indeed, there is now no technical obstacle which prevents the construction and operation of an unmanned ship. With this knowledge perhaps the time has come to reflect on the wisdom of excessive enthusiasm for technological innovation and to consider objectives.

It seems appropriate first to define and explain the term Area Navigation that lately has almost become a slogan in discussions on short-range radio navigation aids. The term itself does not convey much because virtually any radio navigation system permits navigation in the area of coverage of the associated ground stations; for a systematic classification of navigation systems, the term Area Navigation (herein called ANAV) is unsatisfactory. It can be understood only in the context of air traffic control requirements. For a long while the requirements of short-range navigation systems were almost exclusively governed by the needs of air traffic control systems based on an airways concept. When during recent years A.T.C. methods became less associated with a fixed route structure, especially in the terminal area, the requirements to be met by a navigation system changed accordingly. There now appears to be a general trend for area navigation capability to become available as a substitute for a point-to-point navigation system.

A situation as presented in the article by Buzek/Wepster (24, 35) is hard to imagine in the quite different atmosphere of another international shipping operation, such as the Continental European river systems of Rhine and Danube.

The following discussion took place at an open meeting of the Technical Committee, held at the Royal Aeronautical Society in London on 20 January 1971 with Mr. H. E. Smith in the Chair, the introductory discussion paper being presented by Mr. W. P. Robinson, Senior Navigation Superintendent of B.O.A.C.

The interest in area navigation has been stimulated by the knowledge that in many areas of the world air traffic density is expected to exceed the capacity of the existing A.T.C. system in the foreseeable future. Nevertheless, it is important to realize that air traffic delays often result from a lack of airport capacity rather than deficiencies in the air traffic services. Airport capacity is a subject in itself; it is our task to examine how we can improve the present A.T.C. system by the use of area navigation.

On page 533 of the October 1970 issue of the Journal (23, 4), the following passage appears:

‘At a recent meeting of the Safety of Navigation Committee of the Board of Trade, those present were advised by the Mercantile Marine Service Association that they had independently circulated a simple form of the present plan and the proposed reversal of routing to some 2300 Masters of their Association. Of the 500 replies received at that time, two-thirds supported the plan for reversal’

A requirement was stated to Brookes & Gatehouse Ltd. by B.P. Ltd. in 1962 for the measurement of velocity of approach, at the instant of impact against the fenders, of large tankers when berthing at a jetty. This information was required for operational research into the design of jetties for the new super-tankers and for ‘post-mortems’ after heavy impact. Experiments were carried out by us at the Fawley terminal of the Esso Company and the first installation was made by B.P. at their Finnart terminal in January 1963. There has been a continuing demand up to the present time by several oil companies, and a dozen jetties in different parts of the world have now been fitted with this equipment.

Turner has chosen in a recent paper to criticize Moss for inaccurate methods and observes that the inherent inconsistencies are ‘educationally objectionable’. However, he who criticizes must be prepared to be criticized in turn, and when a computer program of the standard evidenced in the printout of PROGRAM 2 is put forward as a general solution to the rhumb-line problem, and one which will enable the navigator to compute his tracks rapidly and accurately, we must needs examine it closely. Such an examination shows that, at the very least, the programmed solution offered is ‘computerizationally objectionable’.

We have not yet heard the full story of the Pacific Glory—Allegro collision and it may be jumping the gun to make any comment, but one thing seems to be clear about the handling of very large single-screw ships. Because of their unwieldiness an avoiding action must be initiated while still at a considerable distance from the threat, if it is to have any effect. This distance is beyond that at which the eye of a navigator can accurately assess the risk of collision or the need to manœuvre. He must, therefore, depend upon instrumental information for making his decisions; in other words, in clear weather as in thick, he must use his radar and plot continuously if he is not to hazard his ship. If the argument is put forward that this will require two men on watch together and that the state of manning does not permit this to be done, the answer is that a change in organization must be made to make it possible.

This paper covers aircraft navigation with emphasis upon self-contained systems, although a survey of the scene cannot avoid reference to external aids. It traces briefly the evolution of self-contained systems since World War II to the present time and then attempts to forecast the way development appears likely to go in the future. The paper deals with both military and civil aviation because, in spite of the increasing importance of the latter, military navigation, as ever, leads the way to improvements for the future.

Anneveld has shown that drift angle due to coriolis may be appreciable in the case of large vessels operating in the middle and higher latitudes. Unfortunately the hydrodynamic information on which he bases his equations is not complete, leading to a false idea of the magnitude of the effect at normal ship operating speeds.