A vessel traffic service is a marine traffic monitoring system established by harbour or port authorities, similar to air traffic control for aircraft. The International Maritime Organization defines vessel traffic service as "a service implemented by a competent authority designed to improve the safety and efficiency of vessel traffic and protect the environment. The service shall have the capability to interact with the traffic and respond to traffic situations developing in the vessel traffic service area".[1][2] Typical vessel traffic service systems use radar, closed-circuit television, VHF radiotelephony and automatic identification system to keep track of vessel movements and provide navigational safety in a limited geographical area.
In the United States, vessel traffic services are established and operated by the Coast Guard Navigation Center. Some services operate as partnerships between the Coast Guard and private agencies.