Studying Conduct in Restricted Visibility
Few conditions test a mariner's judgement like poor visibility. When fog closes in, or when heavy rain and snow reduce what the eye can see, the familiar picture of ships in sight of one another disappears. The rules of the road recognise this, and they set aside a distinct part of the collision regulations for it. For anyone studying seamanship, understanding how reduced visibility is treated is an important step in learning the wider subject.
This guide offers a conceptual overview of why restricted visibility is studied as its own topic, and how it connects to the study of radar. It is written as background reading for revision rather than as operational guidance. The aim is simply to help you frame the subject clearly before you turn to the official texts and the approved training that govern real practice.
A Special Situation
The COLREGs, formally the International Regulations for Preventing Collisions at Sea, arrange their steering and sailing rules by circumstance. Some apply when vessels are in sight of one another. A separate part deals with what happens when they are not, when vessels are navigating in or near an area of restricted visibility. Studying the rules means recognising that this distinction exists and appreciating why it is drawn. The essential idea is that a vessel which cannot rely on sight must think about others in a different way.
What The Topic Covers
In broad terms, this part of the rules is about caution. It concerns matters such as proceeding at a speed appropriate to the conditions, keeping a proper lookout by every available means, and giving careful consideration to any vessel that is detected. Because so much rests on sound judgement, it is one of the areas where study rewards patient, repeated revision rather than the memorising of a single answer. The regulations set out principles; applying them at sea is a skill built through approved training.
Where Radar Study Fits
In clear weather, the eye does much of the work of keeping a lookout. In poor visibility, radar becomes one of the main ways a watchkeeper builds a picture of what lies around the vessel. This is why the study of restricted visibility and the study of radar sit so naturally together. Learning to interpret what a radar display might show, how a contact appears and how its motion can be read, helps a student appreciate what using all available means can involve.
Studying The Rules
The Maritime Master COLREGs app is built as a study companion for this kind of learning. It presents all of Rules 1 to 38 and the annexes in plain English alongside the convention wording, so you can weigh the formal text against a clearer explanation. It offers risk of collision cards, scenario diagrams, a night lights view, and quizzes and flashcards for revision. For the restricted visibility topic, that lets you read the relevant rule, revisit the wording, and test your recall. The app is a one-time purchase, is designed for study only, and is available on the Apple App Store for iPhone and iPad.
Practising With Simulated Radar
The Maritime Master Radar app approaches the same subject from the practical side of reading a display. It is a radar simulator for learning and revision, offering relative and true motion, ARPA practice, a simulated AIS overlay, procedurally generated watches, guided training packs, and debriefs. Because poor visibility is when radar matters most, its simulated scenarios let you practise interpreting a picture in conditions where sight alone would not be enough. Everything is simulated, with no connection to real radar, AIS or GPS. The app is free to download, with optional Pro and Pro Max subscriptions, and is on the Apple App Store for iPhone and iPad. It must never be used for real navigation or collision avoidance, and it is not a substitute for an approved radar or ARPA course.
Bringing The Two Together
Used side by side, the two apps cover two halves of one topic. The COLREGs app helps you learn what the rules say and why restricted visibility is a special case, while the Radar simulator builds familiarity with the kind of picture poor visibility can produce. Neither replaces the official regulations or approved training.
For Study Only
These apps are study, learning and revision aids only. They are not for real-world navigation, and they are not a substitute for approved training or equipment. Nothing here is operational guidance or an emergency procedure. Real navigation, including any decision about collision avoidance in restricted visibility, is governed by the official COLREGs, up to date charts and publications, a proper lookout, and formal approved training. Use these tools to study and revise, and rely on the official sources and your instructors for anything that happens at sea.
