What the examiner is really probing
The examiner wants to know you understand your legal obligations as Master—not just COLREGS Rule 10 as a watchkeeper reciting bullet points, but whether you can manage passage planning, watchkeeping allocation, VTS compliance, and the exercise of command judgement in high-traffic, constrained environments. At command standard you must also show you understand why the rules exist and what discretion, if any, remains with you.
Traffic Separation Schemes — COLREGS Rule 10
Rule 10 applies in TSS areas adopted by IMO. The core obligations:
- Join or leave at the termination, or join from the side at a small angle to the general direction of traffic flow.
- Proceed in the appropriate traffic lane in the general direction of flow.
- Keep as far as practicable from the separation line or zone.
- Avoid crossing if possible; if obliged to cross, do so on a heading as nearly as practicable at right angles to the general direction of traffic flow — this minimises crossing time and makes your intentions unambiguous.
- Inshore traffic zones: use them only if your destination is in or near the zone, you are joining/leaving a lane, you are in an emergency, or you are a fishing vessel operating inshore.
Rule 10 does not relieve any vessel of obligations under any other rule — particularly the steering and sailing rules. A vessel in a TSS is not automatically privileged.
Small vessels (<20 m) and sailing vessels shall not impede power-driven vessels following a traffic lane — "shall not impede" is an active obligation, not merely a preference.
Command-Level Considerations
Passage planning into a TSS: Under SOLAS V/34, your passage plan must identify TSS areas and the associated watchkeeping and speed requirements. As Master you are personally responsible for approving the plan.
Watchkeeping allocation: STCW requires adequate rest and a competent officer on watch. In a busy TSS you should consider: double watchkeeping, your own presence on the bridge, reduced speed to provide more reaction time, and radar/AIS watch assignment as a secondary lookout function.
VTS (Vessel Traffic Services): These operate under SOLAS V/12. Where a VTS is mandatory (compulsory participation schemes are notified in Notices to Mariners and ALRS Vol 6), compliance is a legal requirement. Obligations typically include:
- Reporting on entry to, and exit from, the VTS area
- Providing identity, position, course, speed, destination, and dangerous cargo information as required
- Maintaining a continuous listening watch on the designated channel
- Reporting any defects that may affect safe navigation
- Following instructions unless they endanger the vessel — the Master's overriding authority to deviate for safety is preserved
If VTS gives an instruction you believe is unsafe: You comply or, if compliance would endanger your vessel, you decline, state your reason immediately on VHF, take the action necessary for safety, and record everything. You do not silently deviate.
How to structure your spoken answer in the oral exam
Anchor every answer in your role as Master: "My obligation under Rule 10 is… my passage plan would address… and as Master I would ensure the watch officer was briefed on VTS requirements and had the relevant ALRS volume extract." Show the examiner you are coordinating across planning, watchkeeping, and communications rather than reciting a list of rules.