Marine Voyage Planning and Routing

Marine voyage planning is the mandatory process of preparing, executing, and monitoring a ship’s passage from berth of departure to berth of arrival. SOLAS Chapter V Regulation 34 requires every ship to have a completed passage plan before departure, covering the entire route. IMO Resolution A.893(21) translates that statutory obligation into operational practice through a four-stage framework: appraisal, planning, execution, and monitoring. The framework applies to all vessels on international voyages, and flag-state guidance extends it to domestic trades in most administrations.

The discipline spans chart selection, no-go area definition, abort-point determination, tidal-window calculations, under-keel clearance assessment, traffic-separation scheme compliance, ships routeing system adherence, and integration with weather routing services that now also carry direct relevance to Carbon Intensity Indicator performance under MARPOL Annex VI. This article covers the regulatory mandate, the four planning stages in operational detail, the ECDIS tools and chart requirements that support them, the ships routeing and reporting obligations, the under-keel clearance and squat considerations that govern shallow-water transits, the connection between weather routing and CII compliance, the bridge-team responsibilities and master’s authority, and the practical limits of any passage plan.

Regulatory mandate: SOLAS Chapter V Regulation 34 and A.893(21)

The legal basis for voyage planning in international shipping is SOLAS Chapter V, Regulation 34 (“Safe Navigation and Avoidance of Dangerous Situations”), which entered force on 1 July 2002 following adoption at MSC/74 in May 2001. The regulation requires, in mandatory terms, that prior to proceeding to sea the master shall ensure that the intended voyage has been planned using appropriate charts and nautical publications, and that all foreseeable risks have been considered.

The regulation’s wording is specific about scope. The plan must cover the voyage “from berth to berth.” There’s no provision for a plan that covers only the ocean passage while leaving port approach uncovered; the obligation runs from the moment the vessel’s lines are slipped to the moment they are made fast at destination. Port approaches, pilot boarding areas, and port fairways all fall within the Regulation 34 perimeter.

IMO Resolution A.893(21), adopted by the IMO Assembly on 25 November 1995 (before the 2002 SOLAS amendment but explicitly referenced by it), provides the detailed operational framework. The resolution opens by noting that the purpose of voyage planning is “to ensure the safety of the voyage from berth to berth,” and it identifies four distinct stages through which every passage plan must be developed and executed. The four stages are not advisory suggestions; port-state control officers and flag-state surveyors treat them as the operational standard against which the adequacy of any plan is measured.

What the STCW Convention adds

STCW 2010 Manila Amendments, in Chapter II (certification standards for masters and deck officers) and Chapter VIII (watchkeeping), embed voyage planning competence as a measurable skill. Officers of the watch must be trained to execute an approved plan, maintain the ship’s position on the chart or ECDIS, and identify when a situation requires the master to be called. The STCW Manila Amendments also require all ECDIS training to include voyage-plan construction and route-monitoring functions, reflecting the industry’s transition from paper to electronic charts as the primary navigation tool. STCW Chapter VIII sets the minimum watchkeeping standards that govern how the plan is monitored at sea.

Applicability and exemptions

SOLAS Chapter V applies to all ships on international voyages except warships, naval auxiliaries, and vessels of less than 150 GT used exclusively in the non-international trade. However, most flag states and port-state control regimes have extended passage-planning requirements to domestic voyages for ships above a certain tonnage threshold. The UK MCA’s MGN 315(M+F), Australian AMSA’s Marine Order 21, and the USCG’s requirements under 33 CFR all contain domestic equivalents that mirror the SOLAS framework closely.

The four stages of voyage planning

The four stages of voyage planning are appraisal, planning, execution, and monitoring. Each stage has defined inputs, outputs, and responsible parties, and together they form a continuous cycle rather than a linear sequence that ends once the ship sails.

Stage 1: Appraisal

Appraisal is the information-gathering stage. The officer responsible for planning the voyage (typically the chief officer) must collect and assess all information relevant to the intended passage before any track is drawn. A.893(21) Section 3 provides the checklist, and the list is long by design: incomplete appraisal is the most common failure mode identified in post-incident analyses by the Marine Accident Investigation Branch (MAIB) and equivalent authorities.

Information sources for appraisal include:

The appraisal stage concludes when the navigator can confirm that all known hazards along the intended route have been identified and that the information needed to plan a safe track is in hand. Any gaps, for example missing chart coverage of an area, must be resolved before the planning stage begins. A.893(21) paragraph 3.2 is explicit: the master must be involved in appraising the voyage even if the detail work falls to the chief officer.

Stage 2: Planning

Planning is the stage at which the intended track is drawn, berth to berth, on the charts or entered into the ECDIS route editor. A.893(21) Section 4 defines what the plan must contain. The key planning elements are:

The intended track and waypoints. The route is drawn on charts of sufficient scale to show all the detail needed for the waters concerned: large-scale charts for port approaches and narrow channels, smaller-scale charts for ocean passages. In ECDIS, the route is entered as a sequence of waypoints with the planned course between each leg and, for critical waypoints, a cross-track distance (XTD) or “safety corridor” within which the system will sound an alarm if the vessel deviates.

No-go areas. Zones that the vessel must not enter are explicitly defined: shoal patches, restricted areas, submarine cable corridors, exclusion zones around offshore installations, and areas where the air draft exceeds bridges or overhead cables. On ECDIS, no-go areas are typically enforced through the safety contour setting (set at the ship’s draught plus a defined UKC allowance) and, where needed, manually entered polygon exclusion zones.

Clearing bearings and clearing lines. A clearing bearing is a bearing to a charted object that, if maintained on the correct side, keeps the vessel clear of a hazard. A clearing line defines the minimum safe distance from a feature such as a headland or submerged reef. These are marked on the paper chart or entered as danger areas in the ECDIS route, providing a geometry-based safety backstop independent of the formal waypoint sequence.

Wheel-over positions. The wheel-over position is the point at which the helm order must be given to initiate a turn, accounting for the vessel’s advance and transfer (turning circle characteristics at the planned speed). A.893(21) explicitly requires wheel-over positions to be calculated and marked, especially at turns in narrow channels or at course alterations with a restricted margin of safety. The calculation depends on the ship’s advance (distance covered in the direction of the original course before the new heading is steadied) and transfer (lateral displacement during the turn). Both are speed-dependent: a tanker at 12 knots has a dramatically different turning circle than the same vessel at 6 knots.

Parallel indexing. Parallel indexing is a radar technique that allows the OOW to monitor the vessel’s cross-track error continuously relative to a planned track. An index line is placed on the radar display parallel to the planned track at a distance equal to the expected range off a prominent radar target. As long as the target’s echo tracks along the index line, the vessel is on track. A.893(21) recommends parallel-indexing techniques as a supplement to the formal track, particularly in areas with restricted visibility where visual marks may not be available.

Abort points. An abort point is a pre-defined position on the approach to a berth, a lock, or a confined waterway at which, if a specified condition has not been met, the vessel must execute a contingency manoeuvre instead of continuing. Typical conditions: tug availability confirmed, pilot boarded, main engine tested and ready, anchor cleared for letting go. The abort point is calculated from the time needed to execute the contingency (typically bringing the vessel safely to an anchorage) given the available sea room. On some complex final approaches, two or three sequential abort points may be defined.

Contingency anchorages. The plan must identify where the vessel can safely anchor along the route in the event of an emergency requiring the voyage to be interrupted. This is not limited to the port approach; ocean-passage plans should identify safe-anchorage options at intervals where they exist, and the plan should note NAVAREA and port-authority emergency contacts relevant to each.

Speed profile and ETA management. The plan specifies the intended speed between each waypoint, the expected fuel consumption, and the ETA at key positions: the pilot boarding ground, the berth, and any interim waypoints where the schedule has commercial significance. Just-in-time arrival, where the vessel adjusts speed to arrive at the pilot boarding ground at the moment a berth becomes available, reducing anchorage waiting time, is now a standard planning element endorsed by the IMO’s Port Call Optimisation Framework. The JIT arrival calculator computes the required speed adjustment from current position to achieve a target arrival time.

Traffic separation schemes and mandatory routing. If the route crosses or uses a TSS, the plan must show compliance with COLREGs Rule 10: joining at the extremity, maintaining the appropriate traffic lane, keeping to the starboard side within a lane, and crossing TSS schemes at as near a right angle as possible when crossing is necessary. Mandatory routing measures (deep-water routes, areas to be avoided, inshore traffic zones) are marked on the chart and incorporated in the track.

Emission Control Areas and regulatory zones. The plan must flag when the vessel crosses into or out of an ECA (MARPOL Annex VI Regulation 14) and the associated fuel-changeover requirement. It must also mark any MARPOL special areas (Annex I, IV, V), the timing of the crossing relative to any mandatory reporting requirements, and any flag-state restrictions on discharge that differ from the MARPOL baseline.

The planning stage is complete when the plan has been reviewed and signed off by the master. A.893(21) Section 4.7 states: “the master shall approve the plan before the voyage commences.” The approval is not a formality; the master’s signature on the plan document (or confirmation in the ECDIS voyage plan log) constitutes the bridge team’s collective agreement that the plan is safe.

Stage 3: Execution

Execution is carrying out the approved plan. A.893(21) Section 5 notes that the plan is not a rigid constraint but an authoritative reference; the OOW must follow it and must also apply seamanship and judgment when circumstances require deviation. The key discipline in execution is that deviation from the plan is a deliberate, documented act, not an unnoticed drift.

The OOW’s responsibilities during execution include:

• Maintaining the vessel’s position by the best available means: GNSS primary, radar parallel indexing and visual bearings for cross-check, depth-sounder as a tertiary check in charted waters where depth contours provide position information.
• Calling the master at every pre-defined master-call point, at every pilot boarding or disembarkation point, and whenever conditions develop that were not anticipated in the plan.
• Updating the ETA estimate at each waypoint. A deviation in ETA of more than 15 to 30 minutes (charterer-dependent threshold) typically requires a commercial notification.
• Monitoring for NAVTEX broadcasts affecting the planned route and taking action on any new warnings or notices affecting navigational safety.

Deviations from the plan must be recorded in the deck log with the reason for deviation and the time at which the master was informed. This is not merely good practice; the deck log is a legal document and, in any incident investigation, the absence of a deviation entry combined with evidence of off-track navigation is taken as evidence that the plan was not being followed.

Stage 4: Monitoring

Monitoring is continuous during the execution stage and does not stop when the vessel reaches open sea. A.893(21) Section 6 defines monitoring as the ongoing comparison of the vessel’s actual position, speed, and heading against the planned track. In practical terms:

• In ECDIS: the route-monitoring function compares GPS position to the planned route at a defined cross-track-error threshold, typically 0.1 to 0.2 nautical miles for coastal passages and 0.5 to 1.0 nautical miles for ocean passages. Deviations trigger an alarm on the ECDIS display.
• On paper charts: the OOW plots a fix at a frequency defined in the plan (typically every 30 minutes in ocean waters, every 10 to 15 minutes in coastal waters, and every 5 minutes on port approaches), compares the position to the planned track, and annotates any deviation.
• The monitoring stage includes weather monitoring: comparing forecast conditions to actual sea state, wind, and visibility, and assessing whether the plan remains safe given the developing situation.

The plan may be amended during the voyage. When a significant change in circumstances makes the original plan inadequate, A.893(21) Section 6.2 requires the master’s involvement in revising the plan before the revised track is followed.

ECDIS: the primary tool for voyage planning

Most cargo vessels on international voyages now use an ECDIS as the primary navigation system, either alongside paper charts or, where flag-state approval has been granted, as the sole chart system. IMO Resolution MSC.232(82) defines ECDIS performance standards; it requires ECDIS to support voyage-plan construction, route monitoring, safety-contour enforcement, and integration with the ship’s AIS, speed log, and gyrocompass.

Route entry and safety checks

An ECDIS voyage plan is entered as a sequence of waypoints with planned track angles and, for each leg, a defined cross-track distance (XTD) that sets the width of the safety corridor. Before the route is activated, the ECDIS runs a route-check that tests every leg against the loaded ENC data: it flags any leg that crosses a safety contour, approaches a hazard, enters an area to be avoided, or passes through a TSS in a non-compliant direction.

The safety contour in ECDIS is one of the most important settings in the entire planning workflow. It is set to the vessel’s current maximum draught plus the planned UKC, and the system uses this contour as the boundary of the navigable area. An incorrect safety contour setting, for example using the ballast draught when the vessel is loaded, is a class-1 navigation safety error. Guidance from the ECDIS article covers the performance standard requirements and type-approval implications in more detail.

Chart updates and T&P notices

The ECDIS is only as good as its chart data. Electronic Navigational Charts (ENCs) must be updated to the current Notice to Mariners issue before the route-check is run on the updated data. Temporary and Preliminary (T&P) notices that affect the planned route but are not yet incorporated in ENC updates must be manually entered as user layers or danger areas. This is a persistent source of planning failures: the route-check returns green, but the chart data is not current for recent hazards.

Integration with AIS and ARPA

Modern ECDIS systems integrate AIS target data and ARPA radar tracks, displaying other vessels’ positions on the ENC. This supports the monitoring function during execution by providing a real-time picture of traffic density in TSS lanes, at pilot boarding grounds, and in port approaches. It does not replace the COLREGS watch obligation; the OOW must still conduct a proper radar and visual watch.

Ships routeing: TSS, ATBAs, deep-water routes, and reporting systems

The IMO’s ships routeing system, established under SOLAS Chapter V Regulations 10 and 11 and administered through IMO resolution A.572(14) as amended, includes several categories of routing measure relevant to voyage planning.

Traffic Separation Schemes

Traffic Separation Schemes (TSS) are the most widespread routing measure. IMO has adopted over 150 TSS worldwide, including the Dover Strait, the Strait of Gibraltar, the Torres Strait, the Singapore Strait, and the Strait of Malacca. COLREGs Rule 10 governs the conduct of vessels in or near a TSS.

The key Rule 10 obligations for planning:

• Vessels proceeding along a TSS lane shall proceed in the general direction of traffic flow for that lane.
• Vessels shall join or leave a lane at the extremity (the “entry” end), or where practicable at the side of the lane, at as acute an angle as possible.
• A vessel not using a TSS shall avoid it by as wide a margin as practicable.
• A vessel crossing a TSS shall do so on a heading as nearly as practicable at right angles to the general direction of traffic flow.
• The scheme’s separation zone may not be crossed except in an emergency or to enter a lane.

These obligations translate directly into waypoint design: the approach waypoint to a TSS must place the vessel at the correct entry angle, and the exit waypoint must be positioned to clear the scheme’s boundary before any course alteration for the onward track.

Areas to be Avoided and mandatory routing measures

An Area To Be Avoided (ATBA) is an IMO-designated zone around a specific hazard (an offshore platform, a marine protected area, an ecologically sensitive sea area) where vessels are prohibited from passing unless they are of a specific type or have special permission. ATBAs in the route must be identified during appraisal and the planned track must clear their boundaries.

Deep-water routes are designated channels in areas where the charted depth outside the channel is insufficient for deep-draught vessels. A fully loaded VLCC transiting the approaches to a major port may have no option but to use a designated deep-water route; the planning obligation is to confirm availability, tidal-window compatibility, and the minimum guaranteed depth.

Mandatory ship-reporting systems

SOLAS Chapter V Regulation 11 requires vessels on certain routes to participate in mandatory ship-reporting systems. As of the IMO Ships Routeing publication (10th edition, 2019), mandatory systems are in force in, among others, the Torres Strait (REEFREP), the Strait of Dover (CALDOVREP), the Gulf of Finland (GOFREP), the Canadian East Coast (ECAREG Canada), and around the coast of Japan. Each system has a defined reporting format, a defined radio guard frequency, and defined reporting points; these must be entered on the voyage plan’s communications schedule.

NAVTEX, the automated narrow-band direct printing service on 518 kHz (international) and 490 kHz (national), transmits navigational warnings (B messages), meteorological forecasts (C messages), and search-and-rescue information (D messages) for NAVAREA sub-regions. The voyage plan should note the NAVTEX stations relevant to the route and ensure the NAVTEX receiver is set to capture broadcasts for all NAVAREAs the vessel will transit.

Under-keel clearance, squat, and tidal-window planning

Under-keel clearance (UKC) is the vertical distance between the ship’s keel and the seabed. In shallow-water transits, UKC is the most physically irreversible variable in the plan: a vessel aground cannot be planning-document its way off the bottom. Most port authorities and pilotage authorities specify a minimum dynamic UKC, expressed either as a percentage of the vessel’s draught (typically 10% to 15% for tidal channels) or as an absolute value in metres.

UKC components

Static UKC at any given position is charted depth minus ship’s draught, corrected for:

• Tidal height above chart datum at the time of transit.
• Squat: the dynamic sinkage caused by the Bernoulli effect at speed in shallow water. As a vessel increases speed in confined or shallow water, the velocity of the water flowing beneath the hull increases relative to the free-stream, generating a low-pressure region that pulls the hull downward. Squat depends on ship form (block coefficient), speed, and the ratio of water depth to ship’s draught. The Barras formula gives squat in metres as approximately $S = C_B \cdot V^2 / 100$ for unrestricted water (with V in knots and $C_B$ the block coefficient), but for confined channels the squat is higher by a factor that increases as the channel cross-section approaches the ship’s midship cross-section.
• Wave-induced motions: heave, pitch, and roll all reduce the minimum instantaneous UKC below the static value. In a 2-metre swell, the effective dynamic UKC allowance needed may be 1 to 1.5 metres more than the static calculation suggests.
• Chart datum uncertainty: depths on older charts may be referenced to Lowest Astronomical Tide (LAT) but with a datum uncertainty of 0.1 to 0.5 metres. On surveys older than 20 years in dynamic sedimentation areas, shoaling may have occurred that is not yet reflected in the chart.

The UKC calculator computes the net dynamic UKC given draught, charted depth, tidal height, and speed-induced squat.

Tidal-window calculation

A tidal window is the period during which the actual water level provides sufficient UKC for the transit. Computing the tidal window requires:

1. The minimum water depth required for the transit, derived from draught plus squat at planned transit speed, plus the authority-specified minimum UKC margin.
2. The predicted tidal height above chart datum from the Tide Tables for the port and date.
3. The duration of the window, which is the period during which the predicted tide is high enough to provide the required depth.
4. The time needed for the transit from the pilot boarding ground to the berth, to confirm that the window is long enough to complete the transit safely.

Tidal windows that are marginal, for example a window of 3.5 hours for a transit that takes 3 hours, must include a contingency analysis: what happens if the pilot boards late, if one engine is unavailable for manoeuvring, or if the tidal prediction is slightly less than forecast? The standard practice is to plan to enter at the window opening to maximise available time, rather than timing the approach for the tidal peak.

Weather routing and the CII connection

Weather routing is the operational practice of selecting and continuously adjusting a ship’s track based on weather forecasts to reduce fuel consumption, voyage time, or heavy-weather exposure. It has been standard practice in the deep-sea commercial fleet since the 1960s, but its integration with regulatory CII compliance has elevated it from a cost-management tool to a compliance measure.

How weather routing integrates with voyage planning

During the planning stage, the voyage officer has two options for obtaining the initial route track: lay it off independently based on the charts and distance considerations, or obtain a recommended route from a weather routing service. For deep-sea voyages (typically over 1,000 nautical miles), most commercial operators instruct the master to obtain a routing recommendation from the contracted weather service before departure. Services such as Applied Weather Technology (AWT), StormGeo (BVS), and Wärtsilä Voyage Solutions use numerical weather prediction models (ECMWF IFS, NOAA GFS) combined with the vessel’s performance polar (a matrix of fuel consumption versus speed, heading, sea state, and wind angle specific to the vessel) to compute an optimum route.

The recommended route is not automatically the voyage plan track; it is a professional recommendation that the master reviews and accepts, modifies, or rejects based on vessel-specific knowledge that the shore-based service may not hold. The IMO guidance on weather routing and the conditions for overriding a routing recommendation in poor-weather situations are covered in MSC.1/Circ.1228 (“Revised guidance to the master for avoiding dangerous situations in adverse weather and sea conditions”).

Once at sea, the monitoring function includes receiving updated routing recommendations from the weather service, typically once or twice per day. Where the developing weather pattern differs materially from the forecast at planning stage, the master may revise the track mid-voyage. Any such revision is documented as a plan amendment.

CII implications of weather routing

The Carbon Intensity Indicator, introduced by IMO MEPC resolution MEPC.337(76) and detailed in the 2022 guidelines at MEPC.352(78), measures CO2 per transport work (grams of CO2 per tonne-nautical-mile for most ship types). The attained CII is calculated from the annual fuel consumption records; routing choices that reduce fuel burn on individual voyages aggregate into an improved annual CII rating.

IMO resolution MEPC.346(78) (the 2022 SEEMP guidelines) explicitly lists weather routeing as an approved operational measure in the SEEMP Part III, the element that requires ships with CII ratings of C, D, or E to demonstrate an improvement plan. A vessel assigned a D or E rating can document the adoption of weather routing as a measurable corrective action. The CII attained figure reflects the annual total.

The practical connection is direct. On a typical long-haul dry-bulk voyage of 8,000 nautical miles carrying 70,000 tonnes, a fuel reduction of 3% through weather routing saves approximately 15 to 20 tonnes of HFO, which at a CO2 conversion factor of 3.114 (Regulation 2) reduces CO2 by roughly 45 to 60 tonnes. Across 20 voyages per year, that is 900 to 1,200 tonnes of CO2, a reduction that can shift a vessel from a D to a C rating at the margins of the threshold.

Emission Control Areas and regulatory zone management

An Emission Control Area (ECA) under MARPOL Annex VI Regulation 14 imposes a maximum sulfur content of 0.10% m/m on fuel oil while the vessel is within the area. The established ECAs as of 2025 are the North Sea ECA, the Baltic Sea ECA, the North American ECA (extending 200 nautical miles from the US and Canadian coasts), the US Caribbean ECA, and the Chinese domestic emission control areas. Additional ECAs in the Mediterranean (adopted by MEPC.83 in 2025, entering force 2025) and elsewhere are being added.

The passage plan must:

• Identify the exact ECA boundary crossing positions on the chart.
• Note the required fuel-changeover time before the boundary is crossed, given the ship’s fuel-oil system characteristics: some vessels need up to 4 hours to purge HFO from the system and stabilise on LSMGO or VLSFO.
• Include a fuel-changeover log procedure meeting Regulation 14.6 requirements (log entry giving the date, time, and GPS position of changeover, and fuel remaining in each tank).

The emission control areas article covers the geographic boundaries, the timeline of ECA designations, and the bunker and record-keeping requirements in full detail.

Bridge team management and master’s responsibilities

A.893(21) is clear that voyage planning is a bridge-team function with specific assignment of responsibility. The chief officer prepares the initial plan; the master reviews, approves, and owns it. The distinction matters: the master cannot delegate the duty to ensure the plan is safe; only the detailed preparation work is delegated.

Master’s overall voyage authority

SOLAS Chapter V Regulation 34-1 (added in 2002 alongside Regulation 34) states that the company, the master, and other parties must not impede the master in taking any decision considered necessary for safe navigation. This provision was a direct regulatory response to commercial pressure on masters to proceed despite unsafe conditions, which featured in several major casualties in the 1990s. The master’s authority to deviate from the plan is absolute; the plan is an aid to safe navigation, not a constraint on the master’s judgment.

The master must be present on the bridge for all passages in restricted waters, during poor visibility, in TSS lanes, and at any waypoint or position the plan designates as requiring the master. The plan’s master-call points must be defined explicitly, not left to the OOW’s judgment about whether a situation has become serious enough to call.

The officer of the watch during execution

The OOW executing the plan is responsible for keeping the vessel on track, maintaining the required lookout by all available means (visual, radar, AIS), and calling the master before the situation deteriorates. The standard of watchkeeping is set by STCW Regulation VIII/2 and the associated STCW Code Section A-VIII/2. An OOW who deviates from the plan without calling the master, except to take immediate action to avoid an immediate hazard, is in breach of both SOLAS and STCW standards.

Pre-voyage briefing of the watch officers by the master or chief officer, reviewing the key elements of the plan (critical waypoints, abort points, master-call points, TSS entry/exit procedures, ECA changeover times), is standard practice and is increasingly required by company SMS documentation under ISM Code requirements.

ISM Code and the Safety Management System

Under the ISM Code (SOLAS Chapter IX, implemented through IMO Resolution A.741(18)), the company is required to establish and maintain a Safety Management System (SMS) that includes procedures for voyage planning. The SMS typically defines a minimum standard for what a passage plan must contain, the approval process, the record-keeping requirements, and the procedure for revising the plan during the voyage. Port-state control inspections under the Paris MOU, Tokyo MOU, and other regional agreements routinely check that voyage plans comply with both the SOLAS/A.893(21) requirements and the company’s own SMS procedures. A deficiency in voyage planning is a frequent PSC finding and, depending on severity, can lead to detention.

Specific planning considerations by voyage type

The four-stage framework applies universally, but the content of the appraisal and planning stages varies substantially by voyage type.

Port approach and departure planning

Port approaches are where the majority of serious groundings and collisions occur. The planning density required for the final 20 to 50 nautical miles is an order of magnitude greater than for the ocean passage. Abort points, wheel-over positions, clearing bearings, pilot boarding arrangements, tug availability confirmation, and berth air-draft and beam clearances must all be worked out before the approach begins. For the first call at a port, a Port Information Document from the agent, the port’s pre-arrival checklist, and the local port authority’s guidance should all be reviewed during appraisal.

Ocean passages: great circle and rhumb line

On long ocean passages, the routing choice between a great circle route and a rhumb line affects both distance and the character of the weather encountered. A great circle route between two points at similar latitudes curves toward the pole, passing through higher latitudes that may have more severe weather. The distance saving of a great circle on an east-west trans-Pacific route at 40°N is typically 100 to 300 nautical miles compared to the rhumb line, but the higher-latitude exposure to North Pacific winter gales may make the rhumb line (or a composite great circle that limits maximum latitude) the weather-optimal choice. The great circle versus rhumb line calculator computes both tracks and the distance difference for any two positions.

Polar voyages and Polar Code planning

Voyages in Arctic or Antarctic waters require additional planning elements under the International Code for Ships Operating in Polar Waters (Polar Code), adopted by MEPC.265(68) for MARPOL provisions and by MSC.385(94) for SOLAS provisions. The Polar Code requires a Polar Waters Operational Manual (PWOM) specific to the vessel and a Polar Ship Certificate. Passage planning in ice-covered waters requires ice-routing services (e.g., from the Norwegian Meteorological Institute’s Polar section or the Canadian Ice Service), specific abort criteria for ice conditions, and contingency planning for the unavailability of icebreaker assistance.

Tanker MARPOL Special Area planning

Voyage plans for tankers trading in MARPOL Annex I special areas (Mediterranean Sea, Baltic Sea, Black Sea, Red Sea, Gulf Area, Gulf of Aden, Antarctic Area, North West European Waters) must incorporate the zero-discharge restriction for oily water: no oily water mixtures may be discharged, even if below 15 ppm, within a special area. The plan must confirm that the vessel’s slop tanks and oily water separator have sufficient capacity for the planned transit duration.

Limitations

A passage plan is a pre-voyage document prepared from forecast information and historical data. It cannot guarantee safety; it establishes a structured approach to managing the known risks.

Weather forecast accuracy degrades at range. A planning-stage weather forecast for the day 7 to 10 ahead carries an uncertainty envelope of 2 to 3 Beaufort force in wind strength and 1.5 to 2 metres in significant wave height. Plans that rely on a forecast 10 days ahead for a critical tidal window are working with information that may be significantly wrong by the time of execution.

Chart accuracy in unsurveyed or undersurveyed waters is not guaranteed. The UKHO’s INSPIRE database flags charts surveyed to pre-modern standards (before the International Hydrographic Organization’s S-57/S-100 era). In areas where surveys are more than 30 years old, particularly in Southeast Asian archipelagic waters, parts of the African coast, and some South American approaches, charted depths may not reflect current seabed conditions. The plan should carry an increased UKC allowance in poorly surveyed areas.

The plan does not substitute for a proper watch. The OOW must maintain a continuous watch and respond to developing situations. A grounding where the vessel was on the planned track but the chart data was wrong, the tide table prediction was inaccurate, or the squat at full speed exceeded the plan’s estimate is still a preventable casualty if the OOW was monitoring depth and had sufficient room to slow down.

Commercial pressure can corrupt plan integrity. Charter-party speed warranties and demurrage clauses create financial pressure to maintain speed in conditions where reduced speed would be safer or more fuel-efficient. The master’s overriding authority under SOLAS Chapter V Regulation 34-1 is the legal backstop, but its exercise depends on a company culture that supports the master’s decision. The ISM Code requires companies to document that no commercial pressure has been applied to prevent the master from taking the decision needed for safe navigation.

ECA fuel-changeover timing is vessel-specific. Published guidance gives indicative changeover times, but the actual time to purge HFO and stabilise the engine on LSMGO or VLSFO depends on fuel temperature, purifier settings, and piping volume. A plan that sets the changeover point to arrive exactly at the ECA boundary leaves no margin for a slower-than-expected changeover. The practical standard is to begin changeover 2 to 4 hours before the boundary, depending on vessel characteristics.

ECDIS route-check is not a substitute for professional assessment. The route-check function in ECDIS tests geometry against the loaded ENC data; it cannot assess seamanship judgments like whether an abort point is correctly positioned, whether the stated UKC allows enough margin for an unusual tidal event, or whether the wheel-over positions account for current set. The OOW must review the plan with the same professional judgment that would apply to a paper-chart plot.

See also

• SOLAS Chapter V: Safety of Navigation: the full text and regulatory history of the chapter that contains the voyage-planning obligation.
• AIS and ECDIS: ECDIS performance standards and the operational requirements for type-approved systems.
• COLREGs Convention: Rule 10 governs conduct in TSS lanes; Rules 4 to 19 govern collision avoidance during execution.
• Weather Routing: numerical weather prediction models, performance polars, isochrone optimisation, and the principal commercial service providers.
• Squat Effect: derivation of squat formulas, the Barras and Millward methods, and canal-effect correction factors.
• Trim Optimisation: the relationship between fore-and-aft trim, speed-power curve, and fuel consumption.
• Emission Control Areas: geographic boundaries, ECA designation timeline, and fuel-changeover record requirements.
• STCW Chapter VIII: Watchkeeping: minimum rest hours, OOW qualification standards, and watchkeeping arrangements during different phases of a voyage.
• Slow Steaming and CII: the speed-to-fuel-consumption cubic relationship and its role in CII improvement planning.
• Voyage Charter Party: speed warranties, deviation clauses, and the charterer’s relationship to the voyage plan.