Crossing the traffic lanes
Traffic separation scheme. Advanced level, about 3 min. COLREGs Rule 10.
The situation
You need to get to the far side of a traffic separation scheme. The southbound lane lies ahead, then the separation zone, then the northbound lane. Ostrava is coming down the southbound lane; Lumen is heading north, away from you. Your present heading crosses the lanes diagonally.
How should you cross the scheme?
- Turn to a heading of 090°: Cross at right angles to the lanes.
- Hold your diagonal heading: The shortest route to your destination.
- Turn north and work across gradually: Merge with the traffic before crossing.
Lookout: Shipping in a lane expects crossing traffic to be quick, predictable and easy to read. Your heading is what other ships see.
The sound answer
Turn to a heading of 090°
Rule 10(c): a vessel obliged to cross a traffic lane does so on a heading as nearly as practicable at right angles to the general direction of traffic flow. That minimises the time in the lane and makes your intention obvious.
Why the other options fall short
Hold your diagonal heading
A diagonal crossing keeps you longer in the lane and makes your intentions harder to read; here it also carries you across Ostrava’s bow. Rule 10(c) asks for a heading at right angles to the traffic flow.
Turn north and work across gradually
Heading north in the western lane means proceeding against its southbound traffic flow, which Rule 10(b) forbids. Cross at right angles instead.
Rule 10 · Traffic separation schemes
Vessels using a lane proceed in its general direction of traffic flow. A vessel shall, so far as practicable, avoid crossing lanes, but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.