A traffic separation scheme or TSS is a maritime traffic-management route-system ruled by the International Maritime Organization or IMO. It consists of two (outer) lines, two lanes, and a separation zone. The traffic-lanes (or clearways) indicate the general direction of the ships in that lane; ships navigating within a lane all sail in the same direction or they cross the lane in an angle as close to 90 degrees as possible.
TSSs are used to regulate the traffic at busy, confined waterways or around capes. Within a TSS there is normally at least one traffic-lane in each main-direction, turning-points, deep-water lanes and separation zones between the main traffic lanes. Most TSS include 'inshore traffic zones' between the (outer) lines and the coast. The inshore traffic zone is unregulated and is not intended to be used for through traffic but rather for local traffic, fishing and small craft. A ship navigating in a traffic-lane should sail in the general direction of that lane. The body of water between two opposite lanes is named separation zone and is to be avoided by vessels travelling within the TSS as far as possible except in certain circumstances such as emergencies or for fishing activities. Where needed there are special zones where a lane splits into two channels: one ongoing and the other to the nearby port(s).
The TSS rules are incorporated in the International Regulations for Preventing Collisions at Sea (Under Part B, Section I, Rule 10- Traffic Separation Schemes). An individual TSS is controlled by a vessel traffic service.