In the basic design of a ship, in addition to the cargo or number of passengers to be carried and the required speed, it is necessary to clearly define which sea areas the ship will navigate and which ports it will use.

The applicable laws and regulations and the required equipment differ depending on the sea areas navigated and the flag State. In addition, conditions at ports, canals, bridges, and other locations impose restrictions on the ship’s length, breadth, draft, and height.

Therefore, when organizing the shipowner’s requirements, the navigation area, whether the ship will engage in international voyages, the flag State, the applicable classification society, and the planned routes and ports of call should be confirmed and reflected in the design conditions.

1.3.1 Navigation Areas and International Voyages

Navigation Areas in Japan

Under the system based on Japan’s Ship Safety Act, navigation areas are divided into four categories—Smooth Waters, Coasting, Near-Sea, and Ocean-Going areas—and standards for structure and equipment are set according to the navigation area.

A navigation area is not simply an expression of the route the shipowner wishes to use; it is also a condition that defines the range within which the ship is permitted to navigate.

Table 1.3-1 Navigation areas in Japan

Navigation area	Overview
Smooth Waters Area	Relatively calm waters defined by law, such as lakes, rivers, and harbors
Coasting Area	A range defined by law, in principle including waters within 20 nautical miles of the coast of Japan
Near-Sea Area	A range defined by law, including the sea areas around Japan
Ocean-Going Area	All waters

Because the boundaries of each area have specific definitions, the area charts and relevant laws and regulations should be checked in actual planning.

In addition, there are Limited Coasting and Limited Near-Sea areas, in which conditions such as the range of navigation are restricted.

For example, the Limited Coasting Area described by the Japan Craft Inspection Organization includes a type that is restricted to the part of the Coasting Area within which the ship can make a round trip from the Smooth Waters Area within two hours at maximum speed. However, conditions differ depending on the type of ship and the applicable system, so it is important not to judge by the name alone.

Confirming Whether the Ship Engages in International Voyages

In addition to the navigation area, it is also necessary to confirm whether the ship will engage in international voyages.

For example, a route connecting domestic ports and a route to foreign ports differ in the convention requirements and certificates that must be confirmed.

Moreover, not all provisions of international conventions apply uniformly to ships engaged in international voyages. The scope of application differs depending on ship type, gross tonnage, date of construction, and other factors, so the judgment must be made against the conditions of each convention.

Therefore, when confirming requirements with the shipowner, it is important to go beyond broad conditions such as “ocean-going navigation” and to identify the intended countries, ports, and routes.

1.3.2 Relationship Between International Conventions, Domestic Laws, and Classification Rules

The rules relating to ships are divided into international conventions, the domestic laws of the flag State, port State regulations, classification rules, and others.

These are interrelated, but they are not the same.

Table 1.3-2 Rules applicable to ships and items to confirm in basic design

Category	Items to confirm in basic design
International conventions	Safety, environmental protection, and other requirements applicable according to ship type and voyage conditions
Laws of the flag State	Ship registration, surveys, equipment, required certificates, etc.
Regulations of port States and navigated sea areas	Operating conditions in that country or sea area, such as port entry, discharges, and reporting
Classification rules	Technical requirements for hull structure, machinery, electrical installations, etc.
Conditions for use of ports and canals	Permissible dimensions, draft, equipment, operational restrictions, etc.

Compliance with classification rules alone does not necessarily mean that all laws, regulations, and port conditions are satisfied. The requirements applicable to the planned ship must each be confirmed.

IMO and International Conventions

The International Maritime Organization (IMO) is responsible for developing international rules on ship safety, protection of the marine environment, and related matters.

Representative examples include the SOLAS Convention on the safety of ships, the MARPOL Convention on the prevention of pollution from ships, the Load Lines Convention, and the Ballast Water Management Convention. Ships subject to these conventions undergo the relevant surveys and obtain the required certificates.

International conventions and their amendments do not apply to all ships immediately upon adoption. Conditions for entry into force and dates of application are specified.

The SOLAS Convention adopts the tacit acceptance procedure, under which an amendment is deemed to have been accepted unless a specified level of objection is received within a set period.

In planning a newbuilding, it is necessary to confirm not only the current rules but also the amendments that will apply by the time of construction and delivery. This is because, depending on the rule, the date of the building contract, the keel-laying date, the delivery date, or another date serves as the basis for determining application.

Whether to adopt rules that have not yet entered into force ahead of time can be considered as a design specification, but compliance with mandatory requirements applicable to the ship cannot be omitted at the shipowner’s discretion.

1.3.3 Flag States and Classification Societies

Role of the Flag State

The flag State is the country in which a ship is registered and whose flag it flies. In international conventions, it is generally referred to as the flag State.

The flag State is responsible for ensuring that ships flying its flag comply with the applicable requirements.

Surveys and the issuance of certificates may be carried out by the flag State itself or delegated to organizations it has authorized. Such an organization is called a Recognized Organization (RO), and classification societies often serve in this role.

When selecting a flag State, in addition to the registration system, taxation, and operational conditions, the applicable laws, the required certificates, and the scope of authority delegated to the classification society to be used should also be confirmed.

Class Surveys and Statutory Surveys

A classification society is an organization that establishes technical rules for hulls, machinery, and other items and verifies compliance with those rules.

Here, it is necessary to distinguish between class surveys, which verify compliance with classification rules, and statutory surveys, which verify compliance with international conventions and domestic laws.

Even when the same classification society handles both, the basis of the survey and the role of the certificates issued are different. The extent to which statutory surveys may be carried out on behalf of the flag State is also determined by the authority granted by that flag State.

In Japan as well, there is a system under which surveys by a classification society replace government surveys for certain ships. However, the scope and conditions are specified, and this does not mean that joining a class makes all government surveys unnecessary.

Major Classification Societies and IACS

The major classification societies include the following.

Table 1.3-3 Major classification societies

Abbreviation / name	Classification society	Country
NK / ClassNK	Nippon Kaiji Kyokai	Japan
LR	Lloyd’s Register	United Kingdom
DNV	DNV	Norway
ABS	American Bureau of Shipping	United States
BV	Bureau Veritas	France
RINA	RINA	Italy
KR	Korean Register	Republic of Korea
CCS	China Classification Society	China

As members of the International Association of Classification Societies (IACS), these classification societies work on harmonizing technical requirements and interpretations of rules. However, this does not mean that all classification rules are identical.

Note that GL (Germanischer Lloyd), which appears in older materials, merged with DNV, and the resulting DNV GL changed its name to DNV in 2021. When listing current classification societies, care should be taken not to list GL as an independent society.

In selecting a class, in addition to the shipowner’s preference, factors such as recognition by the flag State, the required class notations, and conditions under insurance, financing, and charter contracts should be organized.

1.3.4 National and Regional Regulations and Approval of Marine Equipment

Even for equipment with the same purpose, the required approvals may differ depending on the flag of the ship on which it is installed and the applicable system.

Confirming these at the basic design stage helps prevent changes after equipment selection and rework caused by missing certificates.

Inspection of Ship Equipment in Japan

Statutory ship equipment installed on Japanese-flagged ships is required to comply with Japanese standards.

ClassNK’s guidance explains that, even for NK-classed ships, conformity of individual items of the relevant ship equipment is verified under systems such as preliminary inspection and type approval by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT).

Therefore, it cannot be concluded that equipment satisfies the conditions for installation on a Japanese-flagged ship merely because it has been approved by a classification society.

EU Marine Equipment Directive: MED

The EU has the Marine Equipment Directive (MED).

The MED is a system that requires conformity assessment in line with international safety and environmental protection standards for applicable marine equipment installed on ships flying the flag of an EU Member State. The equipment covered includes life-saving appliances, fire protection equipment, and navigation equipment, among others.

Applicable equipment that has undergone the prescribed conformity assessment bears the wheel mark, a stylized ship’s wheel.

The MED does not uniformly require all foreign ships entering EU ports to carry MED-certified equipment. It is important to confirm the applicable ships and equipment and to select the approvals required for the ship on which the equipment will be installed.

UK Marine Equipment Approval

The UK also has a conformity assessment system for marine equipment for UK-flagged ships.

The Maritime and Coastguard Agency (MCA) publishes guidance on performance and testing standards, approval procedures, conformity marking, and other matters for applicable equipment. The Red Ensign mark is used as the UK conformity mark.

When selecting equipment for UK-flagged ships, it is necessary to confirm the relationship with the EU MED, the conditions for accepting other certifications, and the requirements applicable at the time of installation.

Regulations for Ships Calling at US Ports

Separately from the requirements of the flag State, the regulations of port States and navigated sea areas must also be confirmed.

For example, the United States has domestic regulations on ballast water management, and foreign-flagged ships are also subject to them. The US Coast Guard (USCG) publishes the relevant regulations and type approval information for ballast water management systems.

Therefore, for ships planned to call at US ports, in addition to approvals under international conventions, the management methods accepted in the United States and the approval conditions for systems should be confirmed.

Both compliance with flag State requirements and the ability to operate at the planned ports of call must be confirmed.

1.3.5 Restrictions on Principal Dimensions Due to Ports and Routes

A ship’s principal dimensions cannot be determined solely by the required carrying capacity. The ability to actually use the planned ports and routes is a prerequisite.

In basic design, items such as the following are organized.

Table 1.3-4 Constraints on principal dimensions and equipment due to ports and routes

Item	Conditions to confirm
Length	Restrictions of quays, anchorages, turning basins, locks, etc.
Breadth	Restrictions of locks, channels, terminal facilities, etc.
Draft	Water depth of channels and harbors, tide level, and required under-keel clearance
Air draft	Height restrictions for passing under bridges and other structures
Arrangement of hull and equipment	Conditions such as interface with cargo-handling facilities, mooring, and use of tugs

Air draft is the height from the waterline to the highest point of the ship. When passing under a bridge, masts, antennas, and similar items must also be included in the check.

In addition, draft and air draft change with the loading condition. Loading cargo increases the draft while reducing the height above the water, so not only the full-load condition but also the light-load condition and ballast voyages should be examined.

Canal Transit Conditions

For ships using canals, not only length, breadth, and draft but also mooring equipment, ship-handling conditions, and other factors must be confirmed.

For example, the Panama Canal Authority publishes “Vessel Requirements,” which summarizes the requirements for ships transiting the canal. At the design stage, the planned transit conditions should be confirmed based on such official materials from the canal authority.

Ship Size Categories Such as Panamax

Terms used to describe ship size include Panamax, Suezmax, and Aframax. These include terms derived from the transit conditions of canals and waterways and terms that categorize ship size by deadweight.

The following table shows the main ship size terms and their meanings.

Table 1.3-5 Main ship size terms and categories

Term	Category / meaning of the name	Description / guideline based on sources
Panamax	Ship size corresponding to the transit conditions of the original Panama Canal locks	Under the Panama Canal Authority’s regulations, conditions are set by length, breadth, draft, and other factors. Transit eligibility is not determined by deadweight alone.
Neopanamax	Ship size exceeding the original Panamax and corresponding to the transit conditions of the new Panama Canal locks	Under the Panama Canal Authority’s regulations, conditions such as length, breadth, and draft are set for the new locks.
Suezmax	Term derived from the largest ships able to transit the Suez Canal	Used mainly as a tanker category. Under the IEA classification, 120,000–199,999 deadweight tonnes.
Seawaymax	Ship size corresponding to the transit conditions of the locks and channels of the St. Lawrence Seaway	The managing organization’s overview materials give maximum vessel dimensions of 225.5 m in length, 23.77 m in breadth, 8.08 m in draft, and 35.5 m in height above the water. Actual transit requires confirmation of the specific rules and approval conditions.
Capesize	Term for large bulk carriers, derived from their use of routes around the Cape of Good Hope owing to canal transit restrictions	MLIT’s port glossary also explains the relationship with the Cape of Good Hope. The origin of the name and the transit eligibility of individual ships today should be considered separately.
Aframax	Tanker size category based on deadweight	According to the EIA, approximately 80,000–120,000 deadweight tons. It is not a term expressing the transit limit of a particular canal.
VLCC Very Large Crude Carrier	Category of large crude oil tankers	According to the IEA, 200,000 deadweight tonnes or more. Those of 320,000 tonnes or more are also called ULCCs.
ULCC Ultra Large Crude Carrier	Category of even larger crude oil tankers among VLCCs	According to the IEA, 320,000 deadweight tonnes or more.

The deadweight ranges for ship size categories differ depending on the source and classification method. For example, the EIA describes Aframax as approximately 80,000–120,000 deadweight tons, whereas the IEA classification uses 75,000–119,999 tonnes. Therefore, when using numerical values, it is necessary to confirm which classification the source adopts.

In addition, the EIA explicitly states that Aframax is not an official category name of AFRA (Average Freight Rate Assessment). Ship size terms and the classification systems used for freight assessment and similar purposes do not necessarily coincide.

It cannot be concluded from the ship size term alone that a ship can use a particular canal or port. Actual transit eligibility should be confirmed based on the ship’s dimensions, draft at the time of transit, equipment, the authority’s approval conditions, and other factors. At the Panama Canal, the permissible draft may be restricted depending on water levels and other conditions, so it is necessary to check both the rules at the time of planning and the notices at the time of transit.

Effects of Shallow Water

In shallow waters, it is necessary to consider not only avoiding contact with the seabed but also the effects on propulsive performance and maneuverability.

Therefore, when comparing the water depth of the planned route with the ship’s draft, the margin required for safe operation should be examined, taking into account ship motions and speed during navigation.

1.3.6 Charter Conditions and Economics

When organizing the shipowner’s requirements, the type of contract under which the ship will be operated should also be confirmed. A time charter, under which the ship is used for a certain period or for a specific voyage, and a voyage charter, under which cargo is carried on a specific voyage, differ in how charges are expressed and how costs are shared.

What Is a Charter Rate?

A charter rate is a term expressing the level of charges for chartering a ship. However, its meaning and unit differ depending on the type of contract, so time charter hire and voyage charter freight must be read separately.

Table 1.3-6 Types of charter contracts and how charges are expressed

Contract type	Overview	How charges are expressed
Time charter	A contract to use a ship for a certain period or for a specific voyage. The shipowner is responsible for employing the crew and maintaining the ship.	Usually expressed as hire per day. Example: US dollars per day.
Voyage charter	A contract to carry cargo on a specific voyage.	Expressed as freight per tonne of cargo or as a lump sum for the entire voyage.
Bareboat charter	A contract to lease the ship itself, under which the charterer is responsible for arranging the crew and managing the ship.	The hire specified in the contract is paid. Because the scope of responsibility for crew and management differs, it cannot be simply compared with time charter hire.

In general, under a time charter, the charterer bears costs such as fuel, port charges, and canal tolls, while the shipowner bears costs such as ship maintenance. Under a voyage charter, on the other hand, the shipowner bears fuel costs and normal port charges. The actual allocation of costs is determined by the terms of the contract.

Relationship Between Ship Size and Charter Hire / Freight

The Baltic Exchange provides assessments of charter hire and freight by ship size and route for bulk carriers such as Capesize and Panamax and for tankers such as VLCC, Suezmax, and Aframax.

These indicators are assessed under defined conditions for the target ships and routes. Therefore, even for ships of the same size category, the value of the indicator does not apply directly to the contract of an individual ship.

In addition, an indicator called TCE (Time Charter Equivalent) is used to compare voyage charter earnings with time charter earnings. It is calculated by deducting voyage expenses such as fuel, port charges, and canal tolls from voyage revenue and converting the result into an amount per day of the voyage.

TCE is not the hire actually paid under a time charter contract. Nor does it represent the final profit after deducting all costs such as crew costs, ship maintenance costs, and financing costs.

Reflection in Basic Design

In basic design, the study includes not only the amount of cargo that can be carried on the planned route but also voyage days, fuel consumption, port charges, canal tolls, and other factors.

For example, when comparing a ship size that can transit a canal with one that takes a detour without using the canal, it is necessary to organize differences in tolls, voyage distance, required days, and fuel costs, in addition to differences in carrying capacity.

In this way, in basic design, the assumed charter contract, the operating route, and the charter hire and freight assumptions used in economic evaluation are often also organized as part of the shipowner’s requirements. In addition to whether the ship can operate technically, whether the planned operation will be economically viable is also a subject of study.

1.3.7 Items to Organize in Basic Design

The shipowner’s requirements are easier to handle as design conditions when they are specified as follows.

• Navigation area and whether the ship engages in international voyages
• Planned routes, port States, ports, and terminals to be used
• Flag State, applicable classification society, and required class notations
• Applicable conventions, laws, and classification rules, and their dates of application
• Approvals and certificates required for marine equipment
• Restrictions on length, breadth, draft, and air draft
• Operating conditions such as full load, light load, and ballast voyages
• Assumed charter contract and the charter hire and freight assumptions used in economic evaluation

If these are not yet determined, the assumed conditions should be stated clearly, and the design should proceed while confirming them with the shipowner.

Beyond satisfying the required carrying capacity and speed, being able to operate in compliance with the rules in the planned sea areas and ports is a prerequisite for the basic design of a ship.

About This Article

References
・Kore Issatsu de Senpaku Kogaku Nyumon [Introduction to Naval Architecture in One Book], edited by the Career Education Research Group of National Colleges of Maritime Technology
・Fune: Hikiai kara Kaisen made [Ships: From Inquiry to Ship Recycling], edited by the Editorial Committee of the Kansai Society of Naval Architects
・Yoku Wakaru Saishin Senpaku no Kihon to Shikumi, 4th ed. [Understanding the Basics and Mechanisms of Modern Ships], by Toyohiko Kawasaki

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・U.S. Energy Information Administration (EIA), “Oil tanker sizes range from general purpose to ultra-large crude carriers on AFRA scale”
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(Last accessed: October 11, 2026)


*This article was compiled based on the author’s understanding and practical knowledge, with reference to the above literature. Actual applicable requirements vary depending on ship type, flag, date of construction, route, and other factors, so the laws, regulations, and guidance of the relevant authorities at the time of planning should be confirmed.