A deckhand at the helm of a towing vessel had fallen asleep before the tow struck a dock near Clatskanie, Oregon last year, the National Transportation Safety Board (NTSB) said on Tuesday, October 8.
The deckhand of the towing vessel Cindy B was experiencing the effects of fatigue while at the helm on November 12, 2023. The towing vessel was pushing the loaded deck barge St John up the Columbia River when the tow gradually moved to starboard out of the channel and struck the Port Westward Beaver Dock. Damage to the dock was estimated at US$6 million.
The deckhand fell asleep during the end of his scheduled night watch, which started at midnight (local time) and ended at 06:00. In addition, he was at a low point in his circadian rhythm and had just transitioned from day to night watches, which changed his awake/sleep cycle.
The pilothouse alerter system in Cindy B did not alarm to wake the deckhand at the helm because a swinging VHF radio microphone was in the motion sensors’ field of view. The swinging microphone tripped the system’s motion detectors and reset the system’s timers.
“A pilothouse alerter, when used as intended, is an effective tool that can help ensure that a crewmember remains awake and vigilant while on duty,” investigators said. “Established procedures for the operation and use of the system, to include measures to ensure the system cannot be unintentionally reset, help ensure that it operates as designed.”
The NTSB report references studies of shift workers that have shown workers on the night shift, similar to mariners on night watches, have a loss of alertness and increased attentional lapses when compared to dayshift workers. In addition to the general increased risk of accidents during a night watch, research of shift workers has shown that there is a greater chance of incidents during the first two nights of a night shift period.
“Disturbances in awake/sleep cycles caused by transitioning from daytime to nighttime watches or shifts result in increased accidents and occupational mistakes,” investigators said. “Although the impacts of these awake/sleep cycle disturbances cannot be fully mitigated, they can be reduced by tools such as pilothouse alerter systems and by allowing longer downtime between watches/shifts.”
Fatigue is often a factor in marine casualties investigated by the NTSB. Mariners should understand the performance effects of sleep loss and recognize the dangers of working on board a vessel while fatigued.
Marine Investigation Report 24-30 is available online.