Radar and the rule of the road at sea

Perhaps the best way of approaching the subject of radar and the Rule of the Road is to enumerate the points which appear to be controversial at the present time. The principle questions are:

1. Is radar detection equivalent to a "sighting"?

1. What is the position of radar in relation to the interpreta­tion of "moderate speed"?

2. Is radar an authorized means of "ascertaining the position" of another ship?

3. Are the movements of a ship which has the echo of another vessel on her PPI, but cannot see her, bound by those ar­ticles of the Steering and Sailing Rules which refer to ships in those relative positions?

Until these matters are specifically dealt with in a revised set of regulations, internationally agreed, the authoritative answers to those questions can only be obtained from judgements delivered on casualty cases which are brought to court. International agree­ment cannot be expected for many years to come, nor have there yet been any judgements which have answered any of these questions specifically. The practical course, therefore, is to see what guidance can be obtained from the current regulations.

The Rule of the Road, constructed many years before radar was thought of, is a remarkable code because it covers an infinite variety of circumstances in very few words. A great deal is left to common sense and the "ordinary practice of seamen," which usually includes consideration for the other vessel and of its probable actions. Although the questions mentioned cannot be answered with authority, they may yet be examined from a common-sense and seamanlike point of view.

Radar detection versus sighting

The great differences between radar detection and visual sighting as a means of observation were discussed in the last chapter; the question is really whether "in radar contact" can be taken to mean the same as "in sight." In the rules sighting is evidently assumed to be mutual but it is quite clear that no such assumption can be made about radar detection. A common-sense view would be that sighting can re­fer only to visual detection and that, for example, the "sound signals for vessels in sight of one another" should not be used in any other circumstances. (Local exceptions to this principle may, however, be found in the regulations for certain inland waterways ) In a collision case in United States waters a vessel was held to blame for using these signals when in radar contact with another ship, but with no ship in sight.

RADAR AND ^MODERATE SPEED"

The possession of radar does not relieve a vessel from the obliga­tion imposed by Article 16 to go at a moderate speed in fog, mist, fall­ing snow, of heavy rainstorms. The question, however, arises whether the use of radar justifies a more liberal interpretation of "moderate speed." What is a moderate speed for one vessel may not be a moderate speed for another vessel in the same circumstances, and it may well Ъе that a radar set properly maintained and properly used might be regarded as a factor which could be taken into account in deciding what is a moderate speed within the meaning of the article. In a col­lision case which came before an Admiralty Court those responsible for the actions of a ship using radar were held to blame for her speed because they were "...not entitled to rely upon the fact that they had facilities of which they made no intelligent use, to excuse them for proceeding in thick fog at a speed which, but for the existence of such facilities, would have been highly excessive." The judge also indicat­ed that the question of a more liberal interpretation of moderate speed in fog when using radar would "no doubt have to be decided in some future case."

The state of weather and sea, the current technical performance of radar and the likelihood of meeting vessels which are poor radar targets are among the factors which must govern the degree of reliance to be placed on radar as an aid to avoiding collision.