Operational Guide · Registers & Logbooks

# Safe Return to Port: The Design Principle for Passenger Ships

After a fire or flooding contained within the design threshold, a passenger ship subject to Safe Return to Port must not merely be safe to abandon: it must be able to return to port under its own power.

Safe Return to Port SOLAS II-1/8-1 SOLAS II-2/21-22 SDC 12

## Operational Explanation

The Safe Return to Port (SRtP) principle, introduced by SOLAS 2010 and codified in regulations II-1/8-1, II-2/21 and II-2/22, requires that a passenger ship, after a fire or flooding contained within a damage threshold defined at the design stage (the "casualty threshold"), be able to return to port under its own propulsion and essential systems, or, if the damage exceeds that threshold, still guarantee a safe and orderly evacuation.

The principle rests on the redundancy of essential systems (propulsion, electrical generation, bilge pumps, communication systems) and on the physical separation of these systems so that a single event cannot compromise them all at once. At SDC Sub-Committee 12 (January 2026) revised Explanatory Notes were agreed, clarifying the practical application of the damage threshold criteria: they will apply to ships with a building contract from 2028, keel laid from 2028, and delivery from 2032.

## Regulatory Reference

SOLAS Regulations II-1/8-1, II-2/21, II-2/22 (SOLAS 2010): Safe Return to Port obligation for passenger ships with keel laid from 1° July 2010, of a length of 120m or more or with 3 or more main vertical zones. Revised Explanatory Notes (SDC 12, January 2026): applicable to building contracts from 2028, keel laid from 2028, delivery from 2032.

## Scope of Application

Passenger ships with keel laid from 1° July 2010, of a length of 120m or more or with 3 or more main vertical zones (in practice, almost every passenger ship over 96m LOA falls under this second threshold).

## Procedure / How to Complete It

1. Verify whether the ship falls within the scope of SRtP based on keel-laying date, length and number of main vertical zones.
2. Consult the ship's design documentation to identify the damage threshold (casualty threshold) beyond which only the orderly evacuation obligation applies, instead of return to port.
3. Periodically verify, through the maintenance programme, that the essential redundant systems (propulsion, electrical, pumps, communications) are kept fully efficient and physically separated as designed.
4. Include SRtP logic in crew emergency management training, so it is clear when an autonomous return is expected and when evacuation should instead proceed.
5. For new buildings contracted from 2028, verify the application of the revised Explanatory Notes agreed at SDC 12.

## Practical Example

Example: after a fire in a technical space contained within the design threshold, the crew of a passenger ship subject to SRtP isolates the damage, verifies that the redundant propulsion and electrical systems (physically separated from the affected space) are still available, and brings the ship back to port without the need for evacuation, in line with the SRtP design logic.

## Real Cases

The Safe Return to Port logic arose from the realisation, gained after several fire and flooding incidents on large passenger ships, that evacuating thousands of people at sea is inherently riskier than keeping the ship able to sail to the nearest port: for this reason the design principle favours redundancy of essential systems over sole reliance on life-saving appliances.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Treating SRtP system redundancy as purely a design feature, without verifying its operational upkeep over time | Progressive degradation of the actual return-to-port capability compared with what was foreseen at the design stage | Include verification of SRtP redundancy upkeep in the planned maintenance programme
Crew not trained on the distinction between the return-to-port scenario and the evacuation scenario according to the ship's design damage threshold | Emergency operational decisions not aligned with the ship's design logic | Train the crew on the specific design damage threshold of their own ship, not on a generic SRtP concept

## PSC Observations

PSCOs may check, for ships subject to SRtP, the design documentation relating to the damage threshold and the maintenance status of the essential redundant systems, particularly after fire or flooding events even if contained.

## Operational Tips

- Know your ship's specific design damage threshold: it is not a uniform concept, it varies from ship to ship.
- Maintain the physical separation of redundant systems as designed: unplanned changes during maintenance work can silently compromise it.
- Train the crew to recognise when an event falls within the SRtP threshold and when it instead requires activation of evacuation procedures.

## Checklist

- Ship's SRtP applicability verified (keel-laying date, length, main vertical zones)
- Design damage threshold (casualty threshold) known and documented
- Essential redundant systems kept efficient and physically separated as designed
- Crew trained on the ship-specific SRtP logic
- For new buildings from 2028, revised SDC 12 Explanatory Notes applied

## FAQ

What is the casualty threshold in the SRtP context?
The damage threshold, defined at the design stage, within which the ship must be able to return to port under its own power; beyond this threshold, the design must still guarantee a safe and orderly evacuation.
Which ships are subject to Safe Return to Port?
Passenger ships with keel laid from 1 July 2010, of a length of 120m or more or with 3 or more main vertical zones.
What did the revised Explanatory Notes agreed at SDC 12 (January 2026) settle?
Clarifications on the practical application of the damage threshold criteria, applicable to building contracts from 2028, keel laid from 2028 and delivery from 2032.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Evacuation Analysis on Passenger Ships Musters and Abandon Ship Drill

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