Vessel Management Tools
There are a number of ways to manage vessel traffic in a waterway. During a PARS, the U.S. Coast Guard will identify which tools work best to maintain a safe waterway for all users. Stakeholders may suggest any or all of the measures discussed below to be included in the Coast Guard’s final recommendations.
A Traffic Separation Scheme north of the Channel Islands of the California coast. Map via NOAA
Routes recommend a safe path of travel in areas with difficult or dangerous navigation.
Traffic Separation Schemes create buffers between lanes of traffic and may include additional navigational guidelines, similar to a divided highway.
Two-Way Routes establish a traveling corridor to provide mariners with an efficient path of travel, minimize turns and junctions, maximize distance from shore, and avoid important subsistence and ecological areas.
Recommended routes are of undefined width, for the convenience of ships in transit, which is often marked by centerline buoys.
Recommended tracks are routes which have been specially examined to ensure so far as possible that it is free of dangers and along which vessels are advised to navigate.
Deep-water routes are within defined limits which have been accurately surveyed for clearance of sea bottom and submerged obstacles have been indicated on the chart.
Mandatory routing systems are adopted by the International Maritime Organization (IMO) and mandatory for by all ships, certain categories of ships, or ships carrying certain cargoes.
Regulated Navigation Areas have established regulations to control vessel traffic within areas determined to have hazardous conditions.
May specify times when vessels can enter, move within, or depart from regulated waters.
May establish limits on size, speed, draft of vessels, or on operating conditions.
May restrict operations to vessels with particular capabilities in hazardous areas or conditions.
Primarily regulate the operation of vessels permitted inside the area, but also may establish control of access to an area if necessary.
Areas to be Avoided in the Aleutian Islands showing high compliance from vessels after their implementation. Image via Aleutian Islands Waterways Safety Committee
Areas to Be Avoided (ATBAs) are areas within defined limits in which either navigation is particularly hazardous or it is exceptionally important to avoid casualties and which should be avoided by all ships, or by certain classes of ships.
Minimize risk of vessels becoming grounded, thereby reducing risk of oil spills.
Facilitate emergency response.
Alert mariners to shoal waters.
Prevents disruption of subsistence activities.
May be mandatory or recommendatory in nature.
In general, ships show high compliance with IMO-designated ATBAs even when they are recommendatory.
Precautionary Areas are areas within defined limits where ships must navigate with particular caution and within which the direction of traffic flow may be recommended.
Often used for turns and junctions in routing systems.
Other measures include:
Electronic navigation aids can relay a vessel’s position and conditions of the weather and sea.
Speed limits can be implemented for safety and security, such as reducing impacts to marine mammals.
A mandatory reporting system is used in the northeast Atlantic to reduce ships strikes on right whales.
Sources and further reading:
Regulated Navigation Areas, NOAA via data.gov
Port Access Route Study: Alaskan Arctic Coast > Definitions, USCG
Ships’ Routeing, IMO
The role of areas to be avoided in the governance of shipping in the greater Bering Strait region, Marine Policy