The alarm cascade: what happens when something really goes wrong

Individual alarms can be managed. The risk on the modern bridge is the cascade: many systems firing at once, often triggered by a shared input like GNSS, with the volume of noise enough to freeze the people trying to respond.

This article looks at how cascading alarms, often triggered by shared inputs like GNSS, can overwhelm bridge teams in the moments that matter most.

The challenges of alarm fatigue and information overload are more obvious when systems are interconnected. For example, Global Navigation Satellite System (GNSS) interference can trigger multiple alerts across a range of systems, including navigation and communication systems.

Barry Hooper, Head of Maritime Strategy at OneOcean, explained that the problem is not always one alarm, but the way alarms can build across multiple systems. “The danger isn’t a single alarm, it’s the cascade. When something really goes wrong, multiple systems alarm at once, and the volume of noise and competing alarms is enough that your body and brain can just freeze.”

Even where alarms are manageable overall, repeated nuisance alerts can still be frustrating in constrained waters. As Hristo Hadzhiev explained, “sometimes we have very annoying alarms, sailing in the Malacca Strait or Singapore Strait, we received that we are heading into danger where there is none.”

The Nautical Institute reported that only 25% reported little to no impact from GNSS disruption, with 75% of mariners reporting moderate to significant increases in workload. This shows that information overload is not just a design flaw but an operational condition that can manifest when systems fail or behave unexpectedly.

The problem is exacerbated by cross-system dependencies, with many platforms relying on common inputs, such as GNSS, so that when these inputs are disrupted, multiple systems can be affected simultaneously.

The Bridge Alert Management standard emphasises prioritisation and relevance, ensuring that alerts enable rapid recognition of abnormal situations. Despite the guidance, many systems still generate high volumes of alerts that do not clearly indicate the next action the crew should take.

This can lead to the crew having to filter information themselves, increasing cognitive load when attention should be focused on decision-making. Alerts should be contextual, highlighting what matters in a given situation rather than presenting all available information equally, allowing crews to prioritise and respond more effectively.