The Waterways Management message can be used to facilitate vessel traffic movement in confined waters. More “directive” than advisory, this message can be broadcast (e.g., information for all ships or a group of ships) or addressed (e.g., information/direction to a single ship). Examples include: lock, gate, narrows, or single passage area.
There are two sub-types of this message; 1) for providing a position/name of the waterway feature, and 2) for providing a list of vessels and their sequence order/times. Specific information for each vessel includes: sequence time, direction, and vessel MMSI. The complete list of message types is contained in Table 5.
- The message can be broadcast or addressed, depending on which alternative is more appropriate.
- If message sub-type 0 is used, then a message sub-type 1 must also be sent to define the position for the sub-type 0 sequence. The message sub-type 1 can be transmitted less frequently than the sub-type 0 if desired.
- The Message Linkage ID can be used to link additional text (e.g., a separate text message). However, the same source MMSI needs to be included in both the Waterways Management and Text Description message.
- If there are no vessels in the queue then the MMSI of 0000000000 can be used for the first vessel with the time being the time of the data report.
- If the MMSI of the vessel is unknown then an MMSI of 1000000003 can be used. An additional text message (with the message linkage ID) can be used to transmit the vessel name as text if desired.
Reporting rate is a function of the number of vessels and how quickly the information changes. Nominally every 5 minutes.