WAYPOINT- Clearing the confusion

01 Oct 2019 The Navigator

Dr Andy Norris, an active Fellow of The Nautical Institute and the Royal Institute of Navigation, takes a closer look at automated alerts and alarms

Automated alerts on vessels contribute greatly towards the avoidance of accidents. They are triggered by systems that are constantly monitoring critical aspects of onboard processes, including those related to navigation, propulsion systems, cargo and security. Of course, all those who use the systems need to understand the audio and/or visual alerts that they generate, and what action to take when they occur.

There are many different types of alert, particularly on the bridge of a vessel. IMO prioritises these by type in its ‘Code on Alerts and Indicators’ (Resolution A.1021(26)), as follows:

Emergency alarms – indicate that there is an immediate danger to human life or to the ship and its machinery and that instant action needs to be taken, for example in fire and water ingress situations

Alarms – indicate situations that require immediate attention and action to maintain the safe navigation and operation of the ship

Warnings – indicate situations that may become hazardous if no action is taken

Cautions – give awareness of conditions that do not warrant an alarm or warning but need appropriate consideration.

Know your alerts and alarms
Emergency alarms indicate highly dangerous situations that are likely to require necessary action by everyone onboard the vessel, such as assembling in a safe area. Relatively few systems onboard a vessel will generated alerts of this type. Fortunately, their actual activation is quite a rare occurrence, except for tests and training.

Conversely, there are numerous systems onboard, especially on the bridge, that can generate the second alert category – alarms. Many of these have a high probability of being activated, particularly those linked to navigation-related equipment. Great care must be taken in deciding upon user settings for alarms. Poor settings can either fail to give an alarm when one is needed or generate lots of unnecessary alarms, making the system less effective in alerting users to more serious situations (See The Navigator, issue 13 – error management).


For example, an ECDIS is required to have alarms for three specific situations:

  • If the safety contour is about to be crossed;
  • If there is a deviation from the defined route;
  • If the Closest Point of Approach limits are breached.

Great care must obviously be taken in choosing appropriate settings.

The third and fourth categories of alerts – warnings and cautions – are far less urgent. They aid the safe operation of a vessel, but do not require an instant response.

Consistency is key
Certain problems can result in numerous alerts being given on the bridge. An extreme example is when a vessel encounters GNSS jamming. Multiple items of bridge equipment rely on GNSS for position and/or timing information and so they all respond with alarms, creating a highly confusing situation for bridge staff, especially when different equipment needs quite different ways of acknowledging the alarm.

To reduce such problems the IMO recommended that from 2014, all new bridges should comply with the standards for Bridge Alert Management as defined within IMO Resolution MSC.302(87). These are aimed at enabling the bridge team on any specific ship to manage all alerts on the bridge in a consistent manner.

The concept includes an optional Central Alert Management Human Machine Interface (CAM-HMI). This is effectively a single-display system that integrates the alerts from all navigation-related systems to help the bridge team rapidly understand any abnormal situation.

In 2018, more detailed technical standards for Bridge Alert Management Systems were agreed as an international technical standard. In future, this will give even greater consistency on how alerts are displayed, acknowledged and analysed.

Unfortunately, older bridges will continue to have the possibility of their users becoming confused when having to handle complex navigation-related alarm situations. In such rare circumstances, key bridge staff must concentrate on deciding and implementing the best emergency course and speed that will reduce all risks, not least by increasing their own awareness of the raw visual scene – that is, what their own eyes tell them.

Contact RIN at: www.rin.org.uk | 1 Kensington Gore, London, SW7 2AT | Tel: +44 (0)20 7591 3134