Collisions and Their Causes – third edition

Thucydides’ wry observation in the fifth century B.C. that “a collision at sea can ruin your entire day” could well be the subtitle of Richard Cahill’s Collisions and Their Causes. The third edition, published by the London-based Nautical Institute after Capt. Cahill’s death, was supervised by Capt. A.N. Cockcroft, whose own work, A Guide to Collision Avoidance Rules, is also a part of the serious mariner’s library.

Despite the explosive growth of technology since the 1950s, collisions continue to occur, and the question why arises with them. Works on the subject consistently refer to the usual suspects of inadequate lookout, failure to take early action based on radar information, inadequate manning and its corollary crew fatigue, and excessive speed for conditions. Cahill pulls no punches in his evaluations and comments, and that’s appropriate given the potential for loss of life and property, serious injury, and ecological devastation.

It may be fair to say that knowledge gleaned from study, enriched by experience and seasoned by judgment leads to safe navigation. One factor overrides all others, however, and that is attitude. If a watch officer operates under the guiding principle of “heads, I’m stand-on; tails, you’re give-way” — whether out of arrogance or ignorance — the outcome will be the same. The author’s observation that “if there is one principle that can be enunciated as the key to collision avoidance it is to ‘treat all vessels encountered with extreme distrust and suspicion'” may not be far adrift.

Early detection resulting from the more widespread use of radar beginning in the 1950s was expected to reduce collisions markedly. In many cases, however, early detection has not achieved the goal of early and substantial action, and vessels continue to steam into close-quarters situations.

Drawing attention to the use/misuse of VHF, the author suggests the role it should play, and at what stage, in collision avoidance. Taking a cue from radar, the phrase “VHF-assisted collision” has entered the maritime lexicon. Beyond language barrier and ship identification (which vessel am I talking with?), the greater threat seems to be timing — continuous attempts to reach a passing agreement when the period for talk has long passed and along with it adequate time for maneuver. The U.K. Maritime and Coastguard Agency Marine Guidance Note 167 cautioned mariners as to the dangers of the use of VHF in collision avoidance, and as recently as June of this year the Maritime and Port Authority of Singapore (Shipping Circular 23) issued the same caution.

“There is no question that the single greatest fault in collision cases is failure to keep an adequate lookout,” Cahill writes. “Adequate” includes not only the human eye and ear but the proper use of radar and evaluation of the data it provides, and as one master observed, a “willingness to look out the window.”

Lurking in the shadow of improper lookout is the manning level of the vessel. Two vessels approaching at night in clear visibility finds the lookout on one vessel below waking his relief while the watch officer is charting a position. Collision, incineration of the entire bridge crew (less one) and loss of the ship ensues. Another in which the master is alone on the bridge at the helm and engine controls — no helmsman, no lookout, no one in the engine room — in poor visibility and proceeding in the wrong traffic lane.

Although the manning level of a vessel is not the only factor affecting the ability to maintain an adequate lookout, it is a critical one, and with the specter of single bridge manning hull-down on the horizon it might be well to consider that “any measure or practice that diminishes the capacity for keeping a lookout should be regarded with great suspicion,” and as Cahill writes further, “the argument for single manned bridges may be eminently sound from a commercial standpoint (ignoring the possibility that it may lead to an increase in casualties), but cannot be sound from the standpoint of safety. It compromises vigilance, and that is a consideration that cannot be dismissed.”

It’s impossible for an OOD/OOW to have experienced every situation under every conceivable condition, but Cahill fills that void. Presenting some 91 incidents occurring under various conditions of visibility, speed, sea state, manning levels, approach aspect, etc., he dissects each episode step by step from initial contact to collision.

Putting himself/herself at the conn, the reader is able to progress through the steps of receiving, assimilating and evaluating information as it becomes available and to decide what action should be taken by each vessel involved. At the end of Thucydides’ fateful day of ruination, decisions made or not made, actions taken or not taken at each stage can be seen through the lens of reality and how each misstep cascaded into disaster. Most instructively, what was it that led each bridge watch to act as they did?

In the preface to this third edition, Cockcroft says, “this is, I believe, the most comprehensive selection of accounts of collisions ever published.” This is borne out not only by the breadth of situations discussed, but the depth of coverage of each circumstance. Not only are the three approach aspects of meeting, crossing and overtaking (with their visibility variations) presented, but subgroups are well covered, such as collisions under special circumstances, getting underway, at pilot stations, at anchor, with tows and those resulting from “interaction” between hulls, bottom and channel margins.

Collisions and its sister publication by Cahill, Strandings and Their Causes, are written specifically for watch standers. The case-study approach of both books makes them ideal for use in classrooms ashore or aboard. The books are available through most maritime bookstores or directly from the Nautical Institute at

By Professional Mariner Staff