The National Transportation Safety Board (NTSB) has released an investigation report on a collision between Big D and Carol McManus Tows, on January 9, 2023.
The incident
On January 9, 2023, the towing vessel Big D was pushing 19 barges downbound on the Lower Mississippi River, and the towing vessel Carol McManus
was pushing 42 barges upbound on the river. At 0152 local time, the two tows collided at mile 312 near Fort Adams, Mississippi, causing the barges in both tows to break free.1 Several barges were damaged in the collision, and about 1,380 gallons of ethanol spilled into the waterway. Two minor injuries were reported. Damages to the barges were estimated at $1.36 million.
Analysis
About 20 minutes before the Big D and Carol McManus tows met at the bend near Fort Adams, Mississippi, the pilots navigating the tows agreed to a port-to-port passage. The Big D pilot then maneuvered his downbound tow toward the right descending bank to set up for the agreed-upon arrangement. However, the Carol McManus pilot “got confused” and incorrectly recalled the arrangement, and, as a result, he navigated his upbound tow toward the right descending bank.
Although visibility was unrestricted as the vessels neared the bend in the darkness, the trees and vegetation along the banks likely obscured each pilot’s view of the other tow until the tows were about 1,100 feet apart. When they saw they were in danger of colliding, the pilots attempted to maneuver to avoid the collision, but there was insufficient time before the tows collided. The Carol McManus pilot stood a 6-hours-on/6-hours-off watch rotation, which can contribute to operator fatigue, but the pilot showed no signs of impairment during the time leading up to the casualty. He responded to radio calls from the Big D pilot promptly and took immediate action once it became apparent that a collision was imminent. The pilot was not impaired by alcohol or other tested-for drugs, nor was he distracted by cell phone use or other causes. He had over 30 years’ experience as a pilot or captain of towing vessels, and thus was sufficiently
experienced and qualified to handle the tow.
After the Big D pilot proposed a port-to-port passage to the Carol McManus pilot, the Carol McManus pilot agreed to the proposed arrangement without
repeating it back. About 20 minutes elapsed between the agreement and the tows meeting. Although the Inland Rules do not require an operator to repeat back a proposed passing arrangement when using radio, verbally repeating or “rehearsing” a piece of information, such as a passing arrangement, serves two purposes: it ensures that both operators understand the arrangement, and it reinforces the storage and maintenance of passing arrangement information in each operator’s working memory until the information is required to be accurately recalled (when the vessels meet). Repeating back a proposed arrangement is critical when there is a long period of time between when passing arrangements are made and when the vessels meet. Had the Carol McManus pilot repeated back the proposed arrangement, he would have been more likely to correctly recall the agreement and maneuver his tow to the left descending bank of the river.
Conclusions
Probable Cause
The National Transportation Safety Board determines that the probable cause of the collision between the Big D tow and the Carol McManus tow was the
Carol McManus pilot incorrectly recalling the agreed-upon passing arrangement, which resulted in the Carol McManus tow encroaching on the downbound Big D tow.
Lessons learned
Repeating Passing Arrangements via Radio
When mariners are making passing arrangements via radio, several factors may impact each mariner’s understanding of the final agreed-upon arrangement.
These factors include garbled radio transmissions, strong accents or an unfamiliarity with the English language, a mariner’s preconceived expectation of the event, fatigue, or distraction. When one mariner proposes an arrangement to another, the other mariner should repeat back the proposed passing arrangement to ensure both parties have a shared understanding of the arrangement. The repeat-back also reinforces the agreed arrangement with each mariner.
