Marine Traffic has Status: "Drifting" and "Stopped" but AIS and COLREGS doesn't

Looking at ship traffic off LA/LB and noticed some ship’s status is given as “Stopped” or “Drifting” From a Marine Traffic website:

Stopped : Get notified when a vessel, that was previously moving , reports speed equal to or lower than 0.5 knots . This notification will remain inactive while the subject vessel is in a port or an anchorage.

Drifting : This notification updates you when our system detects that your selected vessel is drifting based on her transmitted speed and heading.

This article Not Under Command by Cambridge University Press: recommends that stopped be added as a Navigation Status option.


10 I think is “wing in ground effect” like these things:

That brings up a question, is 99 knots the highest speed AIS can report? I was once quite puzzled to see a target approaching at 99 knots that crossed dry land before passing me, it was a C-172 aircraft with AIS. I couldn’t tell if the airplane was actually going 99 knots or if the AIS system couldn’t deal with a higher speed, flat out the plane can do 110-120 or so.

Back to the original issue - if I am “stopped” but have engines running and the bridge manned, I could move if I wanted to. If I am stopped because the engines died, that would be Not Under Command. Is “stopped but under command” a separate thing in the COLREGS and on the AIS?

COLREGS uses “stopped” in Rule 35 - in restricted visibility for vessels not making way. I don’t think it would be very useful in most cases to have a “stopped” status on the AIS.

The AIS status “Drifting” would be useful however for vessels with low-speed diesel engines with unmanned engine rooms that are drifting with the engine shut down. There are hundreds of vessels doing just that at any given time, waiting for a berth or orders etc but there is no officially sanctioned way of signaling that status in the COLREGS or with AIS.

Currently drifting status is commonly signaled by leaving the running lights on as required but turning on all deck lights. It’s not uncommon for vessels drifting to show NUC lights / AIS status even though technically they don’t meet the requirements for NUC.

It beats anchor lights though, NUC might move and one assumes an anchor light = anchored.