Coast Guard: Half of towing vessels transmitting incorrect AIS data


A recent U.S. Coast Guard blog post paints a sobering picture of faulty data transmissions from automatic identification systems (AIS) on the nation’s towing vessels.

In June, more than 50 percent of towing vessels operating in U.S. waters transmitted incorrect AIS data, and “an alarming number of these vessels did not accurately report their dimensions or broadcast a properly assigned MMSI (Maritime Mobile Service Identity) number,” wrote Lt. j.g. David Turay on the Coast Guard Maritime Commons website on July 3.

Failure to accurately report a vessel’s dimensions significantly increases the risk of collision, especially in congested waterways or during low-visibility conditions, Turay said.

“Knowing the location of the bow in addition to the overall length of the vessel and associated barges is crucial to help approaching vessels react and maneuver appropriately,” he said. “This is especially important when visibility is limited.”

In July, Subchapter M went into effect for the nation’s maritime towing industry, requiring vessel AIS to be effectively maintained, including the broadcast of a properly assigned MMSI and other data fields. While the numbers seem to suggest a growing danger, Turay said the Coast Guard is not aware of any accidents caused by inaccurate data transmissions to date.

While proper transmissions are obviously preferred over the alternative, AIS is far from the only safety device available to vessel operators, said Caitlyn Stewart, director of regulatory affairs for the American Waterways Operators (AWO).

“Inaccurate data transmission is a definite concern, but it’s important to remember that AIS is just one of many tools being used for vessel safety,” she said. “And there’s also a person in the wheelhouse who is looking out the window and assessing conditions and the operating environment.”

Stewart said that implementation of Subchapter M did not change the March 2015 requirement that towing vessels over 26 feet and 600 horsepower carry AIS. But it does serve as a reminder about how important it is to make sure that vessel data is properly transmitted, and it puts operators on notice that they could face penalties if they don’t, she said.

Stewart said the AWO is “doing what we can do” to promote proper AIS data transmission, including working with the Coast Guard Navigation Center (NAVCEN) and communicating directly with AWO members via newsletters and alerts.

The Coast Guard also is making it a priority to better inform vessel operators, Turay said. One way is by creating an AIS Encoding Guide and setting up a Web-based tool that allows operators to see the data they’re transmitting and make corrections as needed.

Under Subchapter M, marine inspectors will be checking to make sure that vessels meet all of the provision’s requirements, including full compliance with AIS carriage rules, Turay said.

“Vessels that fail inspection and fail to resolve noted deficiencies within a prescribed timeline may be subjected to fines and/or penalties,” he said. “However, certain serious deficiencies will need to be rectified prior to a vessel’s departure.”

AIS carriage requirements for each vessel class are detailed on NAVCEN’s website,

By Professional Mariner Staff