SOLAS Chapter XI-1 ("Special Measures to Enhance Maritime Safety") was added to SOLAS to improve the safety of shipping through better identification and tracking of ships and enhanced information. Its key provisions:

• Ship Identification Number: every ship of 300 GT and above engaged in international voyages is assigned a unique, permanent IMO ship identification number, marked on the hull/interior and in documents, so there is a unique identifier.
• Continuous Synopsis Record (CSR): intended to be like a ship's "identity card"/passport - it records the ship's history (identity, owner, manager, flag, port of registry, classification, certificates, and any changes), maintained and updated by the Administration, giving a continuous record of the responsible parties.
• Port State Control measures: the chapter also incorporates/refers to enhanced port State control verification (the right of the port State to verify the CSR and that the responsible parties are identifiable) - it underpins the ability of PSC to identify the ship and its operators.
• (The Chapter also includes the "Company and registered owner identification" requirements, and provisions related to the ISM/reciprocal acceptance and to the "ship seldom calling").

Purpose: to establish a clear identity and a documented, verifiable history (owner, manager, flag) of every ship, removing "flags of convenience"/anonymous operations, so that enforcement, PSC, and casualty/pollution responsibility can be effectively assigned and the ship cannot easily change nationality, name or ownership to avoid liability. It thereby enhances maritime safety and the effectiveness of international regulation.

• Ship identification number: The IMO number is to be permanently displayed on the hull (visible both sides/freeboard), on the interior, and in the vessel's documentation (certificates, CSR). It enables positive identification of the ship regardless of name/flag changes, preventing ships from "disappearing" and evading responsibility.
• Continuous Synopsis Record (CSR): contains the ship IMO number, name, owner/registered owner, manager (DPA details), flag/port of registry, classification, certificates (validity), a chronological record of changes (each change endorsed by the Administration), and the particulars of the ISM company. It must be kept on board, updated on every change, and be carried; it provides a continuous, certified history of the ship and its responsible parties.
• Port State control: the port State may verify the CSR, the ship identification number, the certificates and that the responsible parties (owner/manager) can be readily identified and contacted; where the identity is not clear or the ship is not verifiably in compliance, the port State can detain; the enhanced PSC also checks the ISM company, security and crew.

How these contribute to safety/security: a unique identity and continuous record prevent a ship from hiding unsafe history or changing flag/name/ownership to escape standards, making it easier for PSC and regulators to track, inspect, and hold the responsible party to account; this deters sub-standard operation and unsafe "phantom" ships, improves the investigation of incidents/pollution, supports accurate and targeted inspections, and strengthens the whole maritime safety and security regime (including under ISPS) because the ship and its actual management are always identifiable.