Service vessels on AIS: pilots, SAR, dredgers and port craft

Which AIS codes count as service vessels

This is our grouping for the role codes: 50 pilot vessel, 51 search and rescue, 53 port tender, 54 anti-pollution equipment, 56 and 57 local vessels, 58 medical transport, plus 33 dredging or underwater operations and 34 diving operations. Each is a fixed meaning, not a family with a cargo qualifier.

Tugs (52) and law-enforcement or military codes (55, 59, 35) have their own pages. Codes 56 and 57 are spare codes the standard leaves for local administrations to assign, so their meaning varies from country to country.

How to spot one on the live map

Service vessels are where the action at a port entrance is. Pilot boats run out to a pilot boarding point, sit briefly alongside an inbound ship, then run back; their tracks are short, fast and repetitive.

Dredgers move slowly back and forth over the same stretch of channel, then make a faster run out to a dumping ground. Search and rescue boats sit at their stations for long stretches and then move fast and directly when tasked.

Open the live map → Positions there are the latest known, with their source and age.

Who has to carry AIS

Service craft are mostly small and work in national waters, so carriage is set by national rules rather than SOLAS. Most pilot and SAR vessels in well-covered areas carry Class A.

The navigational status to expect

Ship type says what a vessel is; navigational status says what it claims to be doing. These are the statuses that normally go with service vessels:

• 0 · Under way using engine
• 5 · Moored
• 3 · Restricted manoeuvrability
• 1 · At anchor

Where the type code misleads

Restricted manoeuvrability, status 3, is the right status for a dredger working or a vessel supporting divers. It is also the status most often left set after the work has finished.

A search and rescue vessel at high speed is not the same thing as a distress alert. Distress beacons — AIS-SART, man-overboard devices and EPIRBs — have their own MMSI formats and navigational status 14.

Lights and shapes

A pilot vessel on duty shows white over red all-round lights (Rule 29). A vessel restricted in her ability to manoeuvre, such as a dredger at work, shows red-white-red all-round lights, or ball-diamond-ball by day (Rule 27). A vessel supporting divers displays a rigid replica of code flag A.

Summary for orientation only. The COLREGs text is the authority; this site is not a navigation reference.

Questions

What is the AIS ship type code for a pilot boat?

Code 50. Search and rescue is 51, port tender 53, anti-pollution 54, medical transport 58, dredging or underwater operations 33 and diving operations 34.

What are AIS ship types 56 and 57?

Both are "local vessel" codes the standard leaves spare for local or national assignment. What they mean depends on where the vessel operates, so we do not read more into them than that.

Is a service vessel a "service vessel" in the offshore sense?

Not necessarily. Offshore supply and platform-support vessels have no dedicated AIS code and often report 90 (other) or a cargo code. This page groups the harbour and safety roles that the standard does name.

Further reading

• AIS ship type codes explained
• AIS Navigational Status Codes: All 16 Explained
• Reading an MMSI: what the nine digits mean
• All 100 AIS ship type codes, one page each
• Port activity index