UK MCA advises on use of VHF radio and AIS

As explained, there have been a significant number of collisions where subsequent investigations have found that at some stage before impact, one or both parties were using VHF radio in an attempt to avoid collision. The use of VHF radio in these circumstances is not always helpful and may even prove to be dangerous.

At night, in restricted visibility or when there are more than two vessels in the vicinity, the need for positive identification is essential but this can rarely be guaranteed and uncertainties can arise over the identification of vessels, correlation and interpretation of messages received.

In addition, valuable time can be wasted whilst mariners on vessels approaching each other try to make contact on VHF radio instead of complying with the COLREG. There is the further danger that even if contact and identification are achieved and no difficulties over the language of communication or message content arise, a course of action might still be chosen that does not comply with the COLREG. This may lead to the collision it was intended to prevent.

Further, AIS has now been installed on the majority of commercial vessels, and has the potential to make a significant contribution to safety. However, mariners on craft fitted with AIS should be aware that the AIS will be transmitting ownship data to other vessels and shore stations. To this end they are advised to:

• initiate action to correct any known improper installation;
• ensure the correct information on the vessel’s identity, position, and movements (including voyage-specific) is transmitted; and
• ensure that the AIS, if being off for any reason, is turned on, at least within 100 nautical miles of the coastline of the United Kingdom.

Summarizing, mariners should note the following important points:

1. Collision avoidance must be carried out in strict compliance with the COLREG. There is no provision in the COLREG for use of AIS information, therefore, decisions should be taken based primarily on systematic visual and/or radar observations.
2. The use of AIS should NOT be considered to replace the need for a visual lookout or use of “all available means”, but must be used to supplement information obtained from systematic radar plotting.
3. The use of VHF to discuss actions to take between approaching ships is fraught with danger and still discouraged.
4. AIS positions are derived from the target’s GNSS receiver, usually GPS. This may not coincide exactly with the target as detected by radar.
5. Faulty data input to AIS could lead to incorrect or misleading information being displayed on other vessels.
6. A recent development of AIS is the ability to provide synthetic AIS targets and virtual navigation marks enabling coastal authorities to provide an AIS symbol on the display in any position. Mariners should bear in mind that this ability could lead to the appearance of “virtual” AIS targets and therefore take particular care when an AIS target is not complemented by a radar target.

Further details may be found herebelow: