Traffic Separation Scheme (TSS)

A Traffic Separation Scheme (TSS) is a maritime navigation system designed to organise the flow of vessel traffic in congested or high-risk areas, ensuring safe passage by separating opposing traffic streams.

A Traffic Separation Scheme (TSS) is a regulatory measure established by the International Maritime Organization (IMO) to enhance maritime safety in areas where vessel traffic is dense or where there is a high risk of collision, such as narrow straits, busy shipping lanes, or approaches to major ports. The TSS divides the waterway into distinct lanes, typically one for vessels travelling in each direction, and may include additional zones for crossing traffic or ships entering or leaving the main traffic lanes. These lanes are marked on nautical charts, and vessels over 20 metres must follow the designated routes unless unsafe.

The primary objective of a TSS is to reduce the risk of collisions by keeping vessels travelling in opposite directions separated and providing clear guidelines for overtaking, crossing, and joining or leaving the traffic lanes. Ships entering a TSS must adhere to specific rules, such as maintaining a steady course and speed and avoiding crossing traffic lanes at shallow angles. Additionally, smaller vessels and those not constrained by their draught are often advised to avoid the TSS altogether to minimise interference with larger ships with limited manoeuvrability.

TSSs are mandatory in certain areas and are enforced by national and international maritime authorities. Non-compliance can result in penalties, and vessels must use modern navigational aids, such as radar and AIS (Automatic Identification System), to ensure they remain within the prescribed lanes.