Traffic Separation Scheme
The IMO routeing measure that separates opposing streams of traffic, how it is adopted, and how COLREG Rule 10 governs conduct inside it.
A traffic separation scheme is a routeing measure that separates opposing streams of traffic by establishing traffic lanes and a separation zone or line between them. It is the most common of the IMO ships’ routeing measures, and conduct inside one is governed by Rule 10 of the COLREGs , which requires a vessel using a scheme to proceed in the appropriate lane in the general direction of traffic flow and to keep clear of a separation line or zone.
A scheme becomes binding through adoption by IMO, not by national declaration. Under UNCLOS article 41 a state bordering a strait may designate sea lanes and traffic separation schemes, but proposals must be referred to the competent international organization with a view to adoption, and only adopted schemes may be prescribed. The Dover Strait scheme, effective from 1 June 1967, was the first, and it was the principal reason Rule 10 was written into the 1972 COLREGs.
Schemes are usually accompanied by other measures: inshore traffic zones between the landward boundary and the coast, precautionary areas where traffic converges, and deep water routes for draught-constrained ships. The full article will cover the measure types and their definitions, the adoption procedure, Rule 10 in detail including the crossing and fishing provisions, enforcement by port state control and coastal-state prosecution, and the major schemes in force.