NTSB investigation yields lessons on shift worker fatigue

Washington — Night or shift workers who don’t get sufficient rest may be unfit to reliably gauge their own fatigue level because of a diminished ability to detect “when their performance is declining.”

That’s according to a recently released National Transportation Safety Board investigation report on a November maritime incident in which a towing vessel collided with a dock on the Columbia River near Clatskanie, OR.

Investigators found that the worker at the helm of the vessel, who had just transitioned from day to night watches, fell asleep at the end of a watch scheduled from midnight to 6 a.m. A pilothouse alerter system aboard the vessel didn’t sound to wake the worker because a radio microphone impeded the motion sensor’s field of view.

A contributing factor to the incident, which didn’t result in any injuries, was fatigue that the worker “did not perceive” because of a compromised wake/sleep cycle and disrupted circadian rhythm.

NTSB cites previous research showing that night shift workers “have a loss of alertness and increased attentional lapses” compared with those working during the day, and are “more likely to be involved in occupational accidents.” Providing more downtime between watches/shifts can help curb this issue, NTSB says.

“Disturbances in awake/sleep cycles caused by transitioning from daytime to nighttime watches or shifts result in increased accidents and occupational mistakes,” the report states. “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.”