AIS navigational status 11: Power-driven vessel towing astern

What status 11 means

A power-driven vessel towing another vessel or object astern on a towline. Added in a later revision of the standard, originally with regional use in mind, so older equipment and older archives may not use it.

What should go with it

Slow — commonly well under normal passage speed.

Navigational status is entered by hand on the bridge; speed, course and position come from a satellite receiver. Read the status as testimony and the rest as measurement. Where they agree you have learned something. Where they disagree, the measurement is usually right.

How it goes wrong

Many towing vessels still report 0 or 3 while towing, because 11 was a late addition. Its absence does not mean a vessel is not towing.

The matching lights and shapes

The AIS status mirrors a state defined in the International Regulations for Preventing Collisions at Sea (COLREGs), which also say what the vessel should display:

Rule 24 — two masthead lights in a vertical line (three if the tow exceeds 200 m), a yellow towing light above the sternlight; a diamond by day if the tow exceeds 200 m.

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

All sixteen codes

For the field as a whole — and how this site handles it — read AIS navigational status codes, all sixteen.