Updated 11 Oct 2019


Modern ships operate with fewer crew members than in the past and it is not unusual for ships to have just a single man on watch in the bridge or engine room at any given times. As a ship’s command and control centre, it is vital that the bridge has a means of alerting officers to problems and also to ensure that when only one person is on the bridge, that person is alert and active.

Bridge navigation watch alarm systems (BNWAS) are intended as a means of preventing incidents such as collisions and groundings when there is a single OOW on the navigation bridge. The idea is that regular alarms and monitoring will alert a distracted OOW or be able to summon assistance if the officer is incapacitated.

Denmark was the first country to require Bridge Watch Alarms some time before they were made mandatory for all flags by the IMO under SOLAS. This highlights that it is often the action by one flag or port state that sets in motion the wheels at the IMO and the development of a global regulation.

By 2008, the IMO had formulated performance standards for BNWAS which are laid down in MSC.128(75). Ships with alarms fitted prior to the standard being agreed may still comply as the IMO standards were based upon existing requirements of certain states. The standards say that the system must monitor the awareness of the officer of the watch (OOW) and automatically alert the master or another qualified OOW if for any reason the OOW becomes incapable of performing his duties. This is done by way of an initial visual alarm and subsequent audible alarms which the OOW must acknowledge within a specified time period. IMO rules state that the BNWAS should be operational whenever the ship’s heading or track control system is engaged, unless inhibited by the master.

On several occasions, the standards refer to the alarm being reset but do not prescribe how the acknowledgement or reset should be made. Following several approaches from industry bodies and governments, the IMO has decided that although a BNWAS with only a reset button will be allowed, they should be avoided. IMO considers it advisable to install systems making use of a combination of sensors to reduce the number of alarms and avoid unnecessary stress and inconvenience to the OOW.

Watching the OOW

As a result, many of the systems being marketed are fitted with motion sensors of one type or another. Passive infrared sensors are popular choices and can be fitted at various places around the bridge. For an operator selecting a BNWAS, it is important to note that the exact interpretation of the performance standards is a matter for the flag state and while most will accept motion sensors this should not be taken for granted.

In some cases where flag states do accept motion sensors there are additional rules that govern their siting and performance. Flag state surveyors and approved recognised organisations should be aware of the requirements for vessels of that flag and efforts should be made to ensure that an otherwise type-approved BNWAS will not be rejected when the Safety Equipment Survey is carried out. Some manufacturers add in extra degrees of sophistication and modes of their own. This has resulted in the incorporation of features such as password protection, automatic activation when the ship’s speed (determined from GPS input) exceeds a fixed rate and the ability to switch between auditory or visual alarms.

Most systems are stand-alone units, but some manufacturers have incorporated their system into a wider alarm device such as a Bridge Alert Management System (BAMS) or even into an integrated bridge system. In units of this kind, there are connections to any number of other systems, bringing all of the alarms likely to sound on the bridge into a single device. It should be noted that the BNWAS performance standards say that the alarms should not be capable of being confused with fire or general alarms used on the vessel.

Interpretation of regulations connected with BNWAS has been variable to say the least. In May 2014 at MSC 93 some changes to the performance standards were proposed with particular regard to the automatic function of some systems which it was decided should no longer be used. Flag states were invited to use the guidance as an interim measure until such time as the performance standards can be reviewed and revised. The guidance is contained in MSC.1/Circ.1474.

The roll-out for mandatory BNWAS on vessels above 150gt has now been completed, ending in 2018.

BAMS – Managing alerts

This is a subject that should not be confused with BNWAS as they deal with very different situations. Unlike BNWAS, which are in place to monitor navigators, the navigators themselves must constantly monitor the proper functioning of the vessel and its equipment.

SOLAS requires many of the systems found on a ship to indicate failures and problems by way of an audible or visual alert on the bridge. Some of these can be found on the equipment itself – especially in stand-alone navigation equipment – while those for watertight doors, fire alarms, steering and the like are generally incorporated into an alarm display located somewhere on the bridge.

These displays are not always in a location that is convenient to monitor while engaged in navigating the ship. It is not uncommon to find that even where the alarms are banked together, the display may be on the back wall of the bridge meaning that monitoring them means the navigator must turn away from what is happening outside the bridge windows.

Another issue with alarms is that the alarm in each individual piece of equipment will have been determined by the equipment maker and can sometimes be difficult to discern under normal conditions. Operationally, when each piece of equipment has a unique alarm that is not integrated into any form of control panel, prioritising alarms is almost impossible.

Integrated bridge and navigation systems that were made possible by advances in electronics and which began to appear over the last two decades or so were seen as being an ideal way of centralising the alarms.

In 2006 when performance standards for integrated systems were being drawn up, alarm management was discussed at NAV 52 and a report by a working group on the subject presented draft standards. Part C of the INS performance standards represents a first draft regarding an alarm management module. The report discussed at the meeting says that: “an alarm management system should harmonise the operation, handling, distribution and presentation of alarms. To avoid further uncontrolled increase of alarms, a set of priorities based on the urgency of the required response is needed to improve the operator’s situation awareness and his ability to take effective action.”

Therefore, in the performance standards a new philosophy is followed for the prioritisation and categorisation of alarms. An ‘alert’ is defined as an umbrella term for the indication of abnormal situations with three different categories of priority of alerts:

  1. Alarms
  2. Warnings
  3. Cautions

The alert management module is developed with a structure and concept extendable to all alerts on the bridge. In the future, the alert management system could be a separate performance standard and could be extended in a second step to include all alerts on the bridge. So the alert management module in Part C is drafted with the layout of independent performance standards. Four years later, the IMO adopted guideline performance requirements that are detailed in the annex to IMO Resolution MSC.302(87).

The IMO has recommended the use of bridge alert management systems to governments for ships flying their flags but has not yet taken the step of agreeing that they should be mandatory. Operators should check with flag states to confirm the requirements for their vessels.

Other documents that should be consulted when investigating BAMS include MSC.252(83); A.694(17) and MSC.1021(26) from the IMO and IEC 61924 ed.2. Since the performance standards are now in force, a BAMS or the BAM Module human machine interface must be type-approved but is not required for mandatory carriage according to SOLAS V/18. If BAM and INS are both installed, alert information must be integrated into a Central Alert Management (CAM)/Human Machine Interface (HMI) in the INS.

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