Fatigue seen as factor in accident involving two Kirby Inland Marine towboats ​

Written by Nick Blenkey
NTSB reports onCarol Jean sinking

Image: NTSB

The National Transportation Safety Board has issued its report on a March 2019 incident involving two 1968-built Kirby Inland Marine towboats, the Dixie Vandal and the Trinity.

At 0408 local time on March 15, 2019, the Dixie Vandal, pushing a partially loaded fuel barge upbound through the Houston Ship Channel, struck the Trinity, and one of its barges, which were moored and preparing to discharge cargo at the Kinder Morgan Pasadena Liquids Terminal in Pasadena, Texas.

The contact caused the Trinity and its tow to shift about 100 feet upriver, breaking the cargo hoses and mooring lines and damaging the facility. About a half-gallon of jet fuel discharged into the channel. No injuries were reported by the crew of five aboard the Dixie Vandal nor by the Trinity’s crew of four.

Damage to the facility and barges amounted to $630,230.

​The National Transportation Safety Board determines that the probable cause of the collision of the Dixie Vandal’s tow with the moored Trinity and tow was the fatigued pilot falling asleep near the end of his 12-hour watch while maneuvering in the Houston Ship Channel, resulting in the loss of control of the vessel. Contributing to the pilot’s fatigue was the extended length of duty through the night and early morning hours and his use of an over-the-counter antihistamine.

Fatigue has long been identified as a factor in marine accidents and the following is taken from the full report:

Fatigue has been recognized as a leading cause of accidents in the transportation industry. There is evidence that fatigue can adversely impact operator performance. Individuals vary in their requirements for sleep in a 24-hour period; however, cognitive function, alertness, and performance are all affected by a circadian process that is optimal on a “day-oriented” schedule. Circadian troughs, or dips, occur when the body has a stronger desire to sleep, which typically occurs between the hours of 0100 and 0500, depending on individual factors. Research has shown, and National Transportation Safety Board (NTSB) investigations have further highlighted, that fatigue-related accidents are more likely to occur at the end of the night or during very early morning hours. The Dixie Vandal tow struck the Trinity at 0408, which, studies have concluded, is a time when the circadian rhythm is at a low. This dip in circadian rhythm often makes a person feel inclined to sleep, even when the person is not overly fatigued. Some effects of fatigue include lapses of attention, diminished decision-making ability, slowed responses, and an inability to concentrate. Of the 14 marine accidents the NTSB has investigated between 2014 and 2019 in which fatigue was found to be a contributing factor, 10 accidents occurred between 0100 and 0600.

The watch schedule for the crew on the Dixie Vandal was 12 hours on and 12 hours off. The pilot had been awake for about 12 hours at the time of the accident and had been on watch for about 10 of those hours. He reported to investigators that he did not feel fatigued that night, and the captain believed the pilot was “upbeat and well aware of what was going on” during his evaluation for watch readiness at 1800. Company policy, which the captain seemingly supported, stated that if the pilot was feeling tired during his watch, he could have contacted the sleeping captain to assist or called the company to provide a relief, but he did not. Self-reported (subjective) alertness, such as the pilot stating that he felt alert and awake for his shift, is often deceptive. Individuals are often not able to judge their own levels of fatigue. Additionally, while the captain had evaluated the pilot for watch readiness, the accident took place 10 hours following that subjective evaluation; thus, that earlier evaluation was not indicative of his alertness before the collision.

Shift work adds more complexity to the circadian process, because individuals have a harder time acclimating when switching from a day shift (or in this case, off-duty) to a night shift, when a crewmember’s entire schedule is flipped from day to night. A 2018 study (Boudreau et. al) conducted on marine pilots working irregular shifts, when shifts were distributed around the clock rather than a fixed or rotating work schedule, reported a prevalence of daytime sleepiness and insomnia. Although the accident pilot had more than a week to adjust to the night shift, his work/rest schedule was shifted in direct opposition to what was considered “normal” for him (in this case, changing from staying awake during the day to sleeping at night) and his circadian process was likely affected, resulting in fatigue and thus reducing performance.

Download the NTSB report HERE

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