High-Efﬁciency Roll-on/Roll-off
Cargo Ship Adapted to MODALSHIFT Policy
TOHRU KITAMURA*1

KEIZO TERADA*1TETSUYA MORI*1

TOSHINOBU SAKAMOTO*2SHIYUUHEI KURIBAYASHI*3

A focal point in logistic industries nowadays is the Modal Shift Policy, a major shift from the current main lines of transport
predominantly by truck to efﬁcient, low-emission mass transit systems such as domestic shipping and rail transport. To promote
this shift, Mitsubishi Heavy Industries, Ltd. (MHI) has developed a large, high-speed, roll-on/roll-off cargo ship capable of ensuring
compatibility between the conﬂicting targets of speedup and fuel economy for domestic shipping (the “RORO ship”). The salientfeatures of the RORO ship include high-speed navigation with a sustained service speed of up to 23 knots, enhanced economicefficiency (powered by a low-speed diesel engine with excellent fuel efficiency as the main engine), reduced environmental load,
higher transport efﬁciency, and an outstanding design enabling the simultaneous mounting of 160 trailers (12m-chassis) and 251
passenger cars.

*1 Shimonoseki Shipyard & Machinery Works*2 Nagasaki Research & Development Center, Technical Headquarters*3 Kobe Shipyard & Machinery Works1Vs 23kt
90.1

8067%

60
54.4
40

2047%
60.0
78%

71%

42.6
New ships (4 ships in total)

166%

Expanded ship size and reduced
fleet size (6 ships to 4 ships)

The top concerns in developing this ship are reduced
navigation time through speedup and an augmented loading
capacity. The following speciﬁcations have been presented
to us as development objectives by the chartering company
and the Ship’s owner.
2.1 Reduced navigation time through speedup
T he clients requested a reduction in the navigation
time from Tokyo to Hakata from 37 hours to 33, based on
deliberations of the operational diagram. Accordingly, aservice speed of 23.0 knots, with a speed increment of about

Vs 20kt

Existing ships (6 ships in total)

2. Development objectives

100

Existing ships (6 ships in total)

Increased transport efficiency, reduced transport costs,
and high-quality services are indispensable to promote themodal shift in the domestic shipping industry while copingwith diversifying needs of cargo owners. Responding tothese needs of the times, Nippon Express Co., Ltd. and MOLFerry Co., Ltd. plan to commence a joint service on a spacecharter base on the Tokyo-Hakata shipping route.
Nippon Express and MOL Ferry have each put RORO
vessels into service. The former has independently assigned
two RORO-container ships every other day on the TokyoHakata shipping route. The latter has assigned four RORO
ships every day on the same route. In the near future, thesecompanies plan to jointly assign four large, high-speed,identical RORO ships for the expansion of their physicaldistribution services.
To develop the RORO vessels, our company has taken
up va r ious tech n ic a l cha l lenges usi ng t he element a ltechnologies we have accumulated in the construction ofhigh-speed ships.

3 knots compared with that of existing ships, has beenpresented as the required speciﬁcation. Concurrently withthis request for speedup, the clients also requested that theoverall fuel oil consumption of the four new ships be reducedby more than 20% compared with the fuel consumption of thesix existing ships.
Figure 1 shows the energ y-saving specif ication for
the new ship in comparison with that for the existingships, where the fuel oil consumption per day required fortransporting 1-ton deadweight is set on the vertical axis.

Fuel oil consumption per day
required for transporting 1-ton deadweight (kg)

1. Introduction

Fig. 1 Required speciﬁcations for energy saving

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 6 (Dec. 2004)

The total fuel oil consumption of the six existing ships per
day required for transporting 1-ton deadweight is about 54 kg
and rises by 66% to about 90 kg if the navigation speed isaugmented by 3 knots. Even if these six ships are reduced
to four ships, the fuel oil consumption is about 60 kg, slightly
higher than that of the six existing ships. The targeted
reduction of fuel oil consumption by about 30% , to about
43 kg, is the required speciﬁcation for the new ship. Morespecif ically, the total f uel oil consumption per day fortransporting 1-ton deadweight of the six RORO ships, withpropulsive performance equivalent to the existing ships, isabout 90 kg, while that of the new ship is reduced by abouthalf, to 43 kg.

basis for the ﬂeet.

3. General description of development
Our company has developed a high-speed, energy-saving
hull form with reduced wave-making resistance, in order
to attain the development targets described in the previous
section. In doing so, we also made serious efforts to improve
the propeller capability by closely considering balancing
with the cavitation and propeller vibratory force. To fulfill

Table 1 Principal particulars

2.2 Enhanced cargo loading capacity via
an expanded vessel size
It is of considerable importance, from the standpoint ofimproved transport efficiency and reduced transport cost,
to expand the cargo transport capacity while reducing thenumber of ships in the ﬂeet.
Given this factor, it has been determined that the existing
ﬂeet of six ships comprising two RORO-container ships andfour RORO ships with respective lengths of 110 -130m is
reduced to four RORO ships. Each of the four RORO ships,
however, is enlarged to a 170m-long RORO ship, thereby
increasing the ﬂeet cargo capacity by about 30% on a weight

Length overall(m)

166.90

Breadth(m)27.00

Depth(m)23.27Deadweight(t)Gross tonnage

abt. 6200
abt. 10500

ComplementCrew
Passenger

1512Vehicle capacity

12-m chassis
Car160251

Service speed(kt)23.0Main engine

9UEC52LSE × 1

Max. output

15 345 kW × 127 min-1

Upper deck
Trailer holdNo.2 deckNo.1 deck

Engine room

Trailer/Car hold• Increased flexibility to enable adjustments invehicle loading amounts

Trailer/Car holdB1 deckB2 deck
Car hold B3 deck

Fin-stabilizer• Rolling reduction (preventionof cargo damage)

Pipe duct• Easier maintenance of the piping line
• Prevention of piping through different
kinds of tanks (Prevention of marine
pollution due to oil leaks)

Pillar-less hold structure• Improved cargo-handling efficiency

Trailer/Car

Trailer/Car

Up

Stern quarter ramp
• Priority loading for trailers
is available via the accessramp to the decks above
the loading deck

Wide-ranging hull form
with 8 trailer lanes• Minimized water ballast due tohigh stability• Sufficient trailer turning clearance• Improved vehicle loading
efficiency

Straight ramp way
arrangement on loading deck
• Improved vehicle loading
efficiency• Improved vehicle operational
performance

Bow quarter ramp
• Priority loading for cars isavailable via the accessramp to decks below theloading deck

Fig. 2 Outline of the arrangement

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 6 (Dec. 2004)

2buoyancy. Next, the bow and stern forms for the hull form
thus identiﬁed were optimized for selection of candidate hullforms. Finally, a single hull form was selected based on theresults of the performance evaluations carried out throughmodel tests with the candidate hull forms selected in theearlier stages.
3.2 Measures for reducing the fuel oil consumptionof main engine
High-speed ships of this design are generally mountedwith a medium-speed diesel engine of the type mounted
on car ferries. As an alternative, we mounted this shipwith a low-speed diesel engine with excellent specific fuelconsumption, by rationalizing the ar rangement of theengine room periphery. The low-speed diesel engine allows
an increase in the power per cylinder versus that of themedium-speed diesel engine, and a reduction of the numberof cylinders in the main engine. This reduces maintenanceworks, saves labor, and improves operational economy.
De -accelerated navigation is compulsor y within theSeto Inland Sea and Tokyo Bay along the Tokyo-Hakata
shipping route where the ship enters service. Hence, themain engine should be operated under a low load. Longduration, low-load operation can lead to several adverse
consequences, including impaired fuel oil consumption,performance degradation, and defective engine combustion.
T his issue has been addressed by setting the low zone
within a range of 10 -20 % of maximum power (equivalentto 10 -14kt) and establishing a system allowing 12-hourcont i nuous operat ion. Figure 4 shows a concept ua ldiagram of the system. In normal operation, fuel is jettedwith two fuel oil injection valves per cylinder through fueloil pumps. In low-load operation, one fuel oil injection valve
is alternately cut off every 90 seconds automatically. The
jet pressure of fuel oil injection valve increases in this state,
improving the combustion inside the cylinders. As a result,f uel oil consumption can be improved even in low-loadoperation.

Fig. 3 Example of computation with CFD

the target fuel consumption, on the top of the improvementsof the hull form and propeller, the engine department shares
the less-than-10% reduction of fuel consumption. And toreinforce the cargo loading capacity, the vehicle loading
space has been expanded by applying a wide-ranging hull
form and ﬁve-layer vehicle holds.
The main particulars of the ship are shown in Table 1
and an outline of the arrangement is shown in Fig. 2
3.1 Hull form plan
The magnitude of hull resistance, especially the wavemaking resistance element, influences the performance ofthe high-speed hull form. In developing the hull form, wetherefore worked to minimize the hull resistance using therapidly evolving techniques of computational ﬂuid dynamics(CFD). Figure 3 shows the estimated results of wavemaking resistance as an example of computation by CFD.
First of all, a series of CFD computations were carried out
for the hull form plan. Through this approach, the hull form
with minimal hull resistance was identified by computing
the effects of many adjustments to the main particulars,such as the ship length, breadth, depth, and center ofCut-off condition of
one fuel oil injection valve
No.1 CYL.

No.2 CYL.

Operating condition of
automatic cut-off valve
for cutting the fuel oil
injection valve
Cutting the fuel oil
injection valve

Entrywayfor fuel oil

Automatic control box
for cutting of the fueloil injection valve

No.3 CYL.

Air pressure signal line
for cutting of the fueloil injection valve
Fuel oilpump

Fuel oilpump

Fuel oilpump

Main fueloil line

Overall control
signal line
Engine control room

Signals required for main engine control,
such as output, revolution, etc.

Overall automaticcontrol box

Fig. 4 Conceptual diagram of the automatic control system for cutting the fuel oil injection valve

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 6 (Dec. 2004)

3Normaloutput– 10%

Plannedvalue
– 10%

2003
/10/162003/10/302003/11/13
2003/11/272003/12/11
2003/12/25
2004
/1/
82004
/1/222004/2/
5

Fuel oil consumption

Main engine power

3.3 Arrangement
As shown in Fig. 2, the ship has five vehicle holds in afive-layer arrangement. These include the No. 1 deck (aloading deck for trailer spaces), the No. 2 deck just above theNo. 1 deck (also for trailer spaces), the B1 deck just under
the loading deck (a space for both trailers and passengercars), and the B2 and B3 decks under the B1 deck (spaces
exclusively for passenger cars).
The No. 1 deck of the loading deck can be boarded fromthe bow quarter ramp and stern quarter ramp.
The bow quarter ramp can be used exclusively for thedecks below the loading deck, while the stern quarter ramp
can be used exclusively for decks above than the loading
deck. This arrangement enhances the efficiency of cargohandling, as the priority cargo handling for passenger carson the bow ramp can be carried separately from the priority
cargo handling for trailers on the stern ramp.
Each of the trailer holds is wide, comprising eight lanes
for trailer loading. The holds are designed with a pillar-lessstructure to improve cargo-handling efficiency and vehicle
operational performance. To apply the pillar-less structure,
special provisions were taken for vibration control, including
a main engine bracing and reinforced hull structures justabove the propeller (as measures for propeller vibratoryforce).
A set of f in-stabilizers is installed near the midshipto protect cargoes from heavy weather. A bow thruster,
two stern thrusters, and a controllable pitch propeller are
equipped to improve the ship maneuverability in harbor.

Fig. 5 Main engine power and fuel oil consumption
in commercial operation(1) T he improved f lex ibil it y of t he operat ion diag ra m
expanded the cargo collection time in large cities: theship’s anchorage time increased by 4.5 hours per day
on average in Tokyo and by 1.0 hour per day on averagein Hakata, compared with the anchorage times of theprevious ships.
(2) The convenience of the daily service between Tokyo andHakata was enhanced (excluding Sundays).
(3) The service area was expanded by the addition of new
mid-calling ports such as Iwakuni, Tokuyama, and Uno.
Based on the improvement of the sea transport service
between Tokyo and Hakata, a sea distribution system fora Hokkaido-Tokyo-Kyushu route was established throughTokyo as a relay station.
T hese improvements in capabilit y for sea transport
service are expected to activate the international physicaldistribution through Kyushu as a prospective distribution
base and gateway for Asian countries.

4. Operational status after actual service
The required operational performance of the ship was
ascertained by various tests during the sea trial conductedon the stocks. The performance is steadily maintained incommercial operation.
Figure 5 shows the main engine power and f uel oil
consumption measured during commercial operation from
October 16, 2001 to February 7, 2002. The data have been
provided by Aki Kaiun Co., Ltd., the owner of ﬁrst ship of theseries of four ships. As shown in the ﬁgure, both the main
engine power and fuel oil consumption fall below the levels
initially planned. The ship owner praised the vessel for
meeting her targets in operational performance in an actual
sea area.

6. Conclusion
With the increasing demand for environmental conservation
amidst energy shortages, and social problems as reduced
urban traffic congestion, the domestic shipping industry isexpected to contribute greatly to the development of Japan’ssociet y and economy through the deployment of ships
with minimal environmental loads and excellent transport
efﬁciency. Under these circumstances, our company takes on
the vital roles of launching ships with outstanding operational
performance and improving physical distribution systems incommunities. Through contributions such as these, we can
support the development of the domestic shipping industry
and help to promote the Modal Shift.

5. Beneﬁts to distribution by sea
The original ﬂeet of six ships was restructured to a ﬂeet offour ships by increasing the size and speed of the vessels. As
a result, the navigation time was shortened by four hours andcargo transport capacity was increased by 30%, as describedin the foregoing.
A ship with the features and performance described above
went into service on the Tokyo-Hakata shipping route, andtransport service on the route was further improved as aresult. To be more precise:

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 6 (Dec. 2004)

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This ships in this series were awarded the associate “Shipof the Year” prize in 2003 and are expected to play importantroles in the future development of sea transport. Severalof their features will be instrumental in promoting theModal Shift Policy, particularly their reduced in navigation
time through high-speed per formance, their improved
economy and reduced environment burden through lowfuel consumption capability, and their improved transport
efﬁciency through expanded ship sizes.
Three new vessels were completed in succession from
September 2001 to December 2001. Commercial operation
has been steadily advancing and taking on efﬁcient patterns
based on the four-ship system since January 6, 2002.
Finally, we would like to express our thanks to thefollowing parties for opening the gates to the production ofthis series of ships:
Japan Railway Construction, Transport and Technology Agency
Nippon Express Co., Ltd.
Nippon Shipping Co., Ltd.
MOL Ferry Co., Ltd.
Aki Kaiun Co., Ltd.
Shunzan Kaiun Co., Ltd.
Hosei Kisen Co., Ltd.
Horie Senpaku Co., Ltd.

Tohru Kitamura

Keizo Terada

Toshinobu Sakamoto

Shiyuuhei Kuribayashi

Tetsuya Mori

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 41 No. 6 (Dec. 2004)

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