Breakthrough in Japanese Railways 7

Conventional Line Speed Increases andDevelopment of Shinkansen
Asahi Mochizuki

This article explains some technical developments in speed

Increasing speeds on conventional lines

increase until the opening of the shinkansen in 1964, centred

In a nutshell, the history of railway technology is the history

on lines belonging to JR companies (formerly Japaneseof increased speeds and enhanced transport capacity.

National Railways or JNR).

Looking at the example of the Tokaido Line, Japan’s main
trunk line, many modifications were constantly being madeIncreasing Speeds on Conventional Lines

to shorten the travel time between Tokyo and Osaka. Even

Non-shinkansen lines (often including non-JR railways) in

However, electrification toward the end of this era madeJapan are commonly called conventional lines. Japan is ait possible to shorten journey times without increasing

mountainous country, and most conventional lines were built

maximum speed (Figure 1).

so, the maximum speed up to the 1950s was 95 km/h.

to the narrow gauge of 1067 mm, but some private lines

The limiting factors were the tractive power of steam anduse standard gauge (1435 mm). When trying to increase

the weak ground under the roadbed, which limited maximum

operating speeds in the era of stream-hauled trains, narrowaxle loads. For comparison, on the standard-gauge Southgauge proved to have intrinsic disadvantages and the many

Manchurian Railway, operating speed of 110 km/h was

curves and grades in Japan’s mountainous areas also

attained by express trains built in 1934 using Japanese

hampered speed increase.

technology. Some speed increase with electric locomotives

Against this background, electric trains—especiallywas possible by electrification, but electrification was notelectric multiple units (EMUs) —seems to offer the greatest

popular for various reasons.

potential for increasing speeds, because the distributed

EMUs, which were mainly used for commuter traffic

powered axles along the train length had advantages inin those days, ran short distances and stopped at many

reducing axle load while increasing tractive effort as astations, so increasing maximum speed had little effect onwhole. Efforts were made in electrification of railways for thatjourney times. However, in the 1930s, government railways

reason, but there were few developments on major trunkcompeted with private railways in a contest of increasedlines before World War II at the request of the military. As aspeeds. After WWII, in the late 1950s, the influence ofconsequence, major speed increases were only achieved

American technologies developed for PCC car finallyon a wide scale as postwar electrification proceeded.

reached Japan, and improvements were made mainly inacceleration and deceleration. Such new technologies,

Speed constraints on conventional lines

coupled with the advantage of light axle load, contributed

Trains on conventional railways (including both JR

to the development of high-speed EMUs for intercity

and non- JR lines) face the constraint of a maximum

services, reaching maximum speeds of 110 km/h first andemergency braking distance of 600 m. In the early days,

then 120 km/h.

this distance was considered the distance at which

With an eye to the future, JNR’s chief mechanicalsignals could be surely seen by train drivers. But today itengineer Hideo Shima (1901– 98) established a study

is to ensure the ability of a train to stop in an emergencygroup on high-speed bogie vibration in 1947 and started

on a line with level crossings. This 600-m limit imposes a

research into speed increases. Shima was a specialist in

maximum speed of 130 km/h due to physical constraints

steam locomotive design. He believed that it would besuch as loss of adhesion between steel wheels and rails

difficult to increase speeds of loco-hauled trains with theirat emergency braking. On lines without level crossings,

heavy axle loads even on standard gauge tracks due tomaximum speeds up to 160 km /h are permitted on an

Japan’s topographical and geological nature. He realized

exceptional basis. Europe does not have such constraints

that increasing the speed of EMUs with light axles was theand 160 km/h is the normal maximum operating speed on

key, and started work on developing high-speed bogies

non-high-speed lines.

for EMUs.

Japan Railway & Transport Review No. 57 • Mar 201142

Breakthrough in Japanese Railways 7

In 19 4 8 , a 19 3 0 s M o ha 52 E M U
reached a maximum speed of 119 km/h
and then a new EMU belonging to Odakyu
Electric Railway set a speed record of 145km/h on the Tokaido main line in 1957. In
1959, a test run using Series 151 EMU

Figure 1 Speed Increases on Tokaido Main Line
Event

Year

0

50

Jul 1889: Line opened between Kobe and Shimbashi

30.1

Sep 1896: Express services started

34.8

100

200 (km/h)

150

Maximum speed (shinkansen)
Maximum speed (conventional line)
Scheduled speed

Apr 1906: Special express services started

44.2

Jun 1912: Limited express services started

47.9

reached 163 km /h, followed by a highspeed test car setting a narrow-gauge
world record of 175 km /h in 1960. The
results of research into high-speed bogies

Aug 1913: Line fully double tracked
Jul 1923: High-performance locomotives introduced

48.9

were utilized in developing high-speed

Dec 1925: Kozu electrified

intercity EMUs such as Series 151, andOct 1930: Super express services started

also became the development foundation

68.2

Dec 1934: Tanna Tunnel completed

69.6

for shinkansen high-speed bogies.
The Series 151 EMU, which attained

57.6

Oct 1943: Super express services stopped

95

65.5
61.8

163 km/h in 1959, was used for limited

Oct 1944: Limited express services stopped
1947: Express service stopped

express services between Tokyo and

Sep 1949: Limited express services restarted

62.1

Osaka. Inaugurated in 1958, it ran 556 km

Oct 1950: Hamamatsu electrified

69.9

between the two cities in 6.5 hours. This

Nov 1956: Entire line electrified
Oct 1958: EMU limited express services started

74.6
81.9

epoch-making EMU was welcomed bysociety as a whole and had a major impact
on development of the shinkansen.

Measures to increase speed ofconventional lines

Sep 1959: EMU limited express journey times shortenedJun 1960: EMU limited express journey times shortened

51.7
39.9

110

83.9
86.0

Oct 1964: Shinkansen opened
Nov 1965: Shinkansen speed increased

128.9

Oct 1968: Conventional line speed increased

120

210
162.8

The success of the long-distance EMU
service between Tokyo and Osaka spreadto other intercity routes across Japan. Many

Nov 1986: Shinkansen speed increased

164.5
179.8

220

of those were achieved thanks to expansionof main line electrification. Much of the new
main-line electrification used alternation
current (AC), so many long-distance dual-current EMUs werebuilt to run through both AC (20 kV, 50/60 Hz) and DC (1.5kV) sections.
Maximum speeds reached 120 km/h by the late 1960s,
but these trains had almost reached their limits in terms ofthe constraint of emergency braking distances of less than
600 m. The maximum speed could only be increased to
130 km, even using anti-slip re-adhesion techniques. Later

Kumoya 93 High-speed Testing Car that Set a Record of 175 km/h(100 Years of JNR Rolling Stock)running tests by the Railway Technical Research Institute

Moha 52 EMU Produced in 1936 

(100 Years of JNR Rolling Stock)

481 Series AC-DC Limited Express EMU  (100 Years of JNR Rolling Stock)

43

Japan Railway & Transport Review No. 57 • Mar 2011

(RTRI) and JR Shikoku verified that maximum speeds up 160

specifications decided in 1941 settled on building a double-

km/h were possible using rail braking, which were common

track with a gauge of 1435 mm, minimum curve radius ofin the USA and Europe at that time, but rail braking was not2500 m, maximum grade of 10 ‰, maximum axle load of 28

put to practical use in Japan for various reasons.

tonnes, and 60 kg/m or heavier rails. Partial electrification

Japanese railways are characterized by many curves

at 3 kV dc was planned. The rolling stock gauge (loading

and grades, so increasing the maximum speed wasgauge) was set at maximum height of 4800 mm andineffective in reducing travel time on most inter city routes.

maximum width of 3400 mm. All trains were to be hauled by

To reduce travel times, the speed in curves and on grades

locomotives, running between Tokyo and Osaka in 4.5 hours

had to be increased, not the maximum speed. As a result,at speeds up to 200 km/h.
Purchase of land started in 1939, and tunnel construction

the development of tilting trains started in the late 1960s.

started in 1941. Construction was abandoned in 1943 due toDevelopment of Shinkansen

worsening war situations.

Measure to increase capacity on Tokaido main line

in 1957, and the government set up a Ministry of Transport

The rapid postwar recovery led to increasing traffic(MOT) panel to investigate the idea. Around the same time,

volumes, and insufficient rail transport capacity soon

RTRI presented a lecture on the technical feasibility of rail

be ca m e m aj o r b ot tle ne cks fo r J apa n’s e c o n o mic

travel between Tokyo and Osaka in 3 hours, and awarenessdevelopment. Above all, by 1955, the Tokaido main lineof high-speed rail spread to the public.

Sogo proposed construction of a high-speed new line

The MOT panel conducted detailed deliberation of thewas facing such severe lack of capacity that anotherhigh-speed new line, and the shinkansen plan was finalized

double-track was thought to be necessary.
A committee was created in 1956 to investigate how toin 1958. It followed the prewar bullet train project in many

increase capacity quickly, and measures such as quadruple

aspects, including the route and technical specifications

tracking or building a new line were discussed. Opinions

such as 1435-mm gauge track, minimum curve radius of

were split, and the easier measure of adding track held the2500 m, and maximum grade of 10 ‰. The new plan targetedadvantage. However, decision by Shinji Sogo (1884–1981,

3-hour journeys between Tokyo and Osaka using EMU trains

appointed JNR President in 1955) to throw out the oldon an AC-electrified track. The construction period was 5

concept and create a more rational system led to favouring

years. The framework was approved by the Cabinet and theconstruction of a new separate line.

plan was put into action in 1959. JNR set up a committee in1958 led by Hideo Shima, who was appointed to JNR Vice

Ideas for the Tokaido Shinkansen

President for Enginnering in 1955, to investigate construction

The quickest and most economical way of building a new

standards that were given provisional MOT approval in 1960

line along the Tokaido route was to utilize the land purchased

and officially adopted in 1962. Construction started in 1959,

and partially constructed tunnels for the so-called ‘bullet

and the Tokaido Shinkansen was completed in 1964.
Sogo did more than just decide on the construction oftrain’ project abandoned in 1943.

a railway with a new system. While not an engineer, he had

The outline of ‘bullet train’ plan is as follows:
The preliminary survey started in 1938. Construction

excellent knowledge of technical subjects, and he madeNew RTRI building Completed in 1959 

Shinkansen Test EMU and JNR President Sogo(History of Technical Development of Tokaido Shinkansen EMU)Japan Railway & Transport Review No. 57 • Mar 2011

(RTRI)

44

Breakthrough in Japanese Railways 7

the decision in 1956 to provide massive funding to the RTRI

requiring enormous power for running faster trains. Adhesion

to provide better research environment. One of the results

between rails and driving wheels transmitting the tractive

was the aforementioned lecture, which is thought to haveeffort also becomes a problem. With a conventional loco-

garnered great support for Sogo’s decision.

hauled train, this can be overcome by making the locomotive

As an aside, two German high-speed test train carsheavier but the high axle loads of heavy locomotives

are famous for having reached 210 km/h in 1903. Thoserequire solid and sturdy tracks that are expensive to build.

were special test cars that collected three-phase AC power

Building such tracks on the weak ground along the Tokaido

from three pantographs, and the rotating speed of 3-

Shinkansen would have been extremely difficult.

phase asynchronous motors was controlled by changing

AC electrification was a solution for providing trains withthe frequency at substations. The system did not comegreater power. Electric power supplied at very high voltage

into practical use due to technical requirements, but

could greatly reduce the current required for high-speed

achieving speeds in excess of 200 km/h at such an earlyrunning, facilitating power collection by trains. Japan had

date was revolutionary. While it may be only a coincidence,just acquired the technology of AC electrification on its own

Yasujiro Shima, leading mechanical engineer of Japanese

account in the late 1950s.

government railways, was at the test runs. Perhaps the

The solution to heave axle loads was switching to

prewar bullet train project headed by Shima was influenced

EMUs with distributed motive power along the train length

by his witnessing the tests and it is fitting that it was his son

producing high traction effort and lower axle loads.

JNR Chief Engineer Hideo Shima who was responsible forAdvances in semiconductors for power supply during thebuilding the Tokaido Shinkansen running at 200 km/h somelate 1950s supported development of AC EMU trains.

60 years later.

Securing high-speed running stability

Shinkansen Technical Issues and their Solutions

The issue of securing running stability was behind theWhile 160 km/h was a common speed in North America

in 1903 so track and bogie modifications were made toand Europe, there were worries about speeds in excess

conquer hunting oscillation. The 1955 high-speed tests inof 200 km/h in those countries. Although the German ACFrance also experienced serious hunting oscillation, leaving

powered test trains described above reached 210 km/h,

the track very deformed after the test train had passed by.

difficulty in reaching 210 km/h with the German test train

In light of these tests, some technology was needed

it was a struggle to overcome the technical barriers.
Another test train set a record of 331 km/h in France in
1955, but limitations pertaining to stable running and powercollection performance were highlighted. We can assume
that challenging technical innovations were thought to benecessary to go any faster.
Aeroplanes and automobile expressways were also
developing rapidly during this time period and the popularfeeling was that the age of rail was coming to an end, so themotivation to seek innovations in railway technology could
have been declining.
Construction of the Tokaido Shinkansen started amidst
this social background. There was no technology anywherein the world offering day-to-day stable operations at speeds
greater than 200 km/h, although the Japanese engineers
had some vague knowledge of the results of the Frenchhigh-speed tests. They rose to challenge of exploring the
unknown ‘territory’ of high-speed operations. The following
looks at their major accomplishments on the path to solving
the many problems.

Issues with traction power and axle load
The basic issues for high-speed operation are securing
power source and transmission of tractive effort. Runningresistance increases at roughly the square of speed,

Shinkansen Bogie Tests on a Rolling Stock Test Stand 

45(RTRI)

Japan Railway & Transport Review No. 57 • Mar 2011to prevent hunting oscillation ofshinkansen running at commercial

Figure 2 Series 0, 100 and 200 Running Resistance Comparison (Outside Tunnels)

speeds and this proved to be the

(N/t)
200

most important issue in developing
shinkansen technology. Hunting
oscillation is inevitable with railway
can be avoided if the speed range
in which hunting occurs could bemade higher than operating speeds.
However, the methods known at thattime was not appropriate for high-150
Running resistancecars due to their structure, but it(1) Series 0 r=11.768 + 0.15200 V + 0.0014347 V2 (N/t)(2) Series 100 r=12.484 + 0.04915 V + 0.0013543 V2 (N/t)(3) Series 200 r=11.523 + 0.15115 V + 0.0008833 V2 (N/t)

(2)

(1)
(3)

100

50

speed bogie design.
A main theme of the study groupon high-speed bogie vibration wasbogie hunting, and research was

0

0

50

100

150

200

250

Speed

already in progress. Theoretical

300(km/h)

analysis and experiments were done
mainly by aeronautical engineers who
had transferred to the RTRI from former
imperial navy research labs. Bogies were designed andthere were no quantitative data, so tentative values wereredesigned for repeated tests using prototype bogies on a

fixed on estimation. Values deduced from running tests oftest stand at RTRI and prototype rolling stock on shinkansen

Series 80 EMUs between 1952 and 1956 were also used.

test tracks. As a result, hunting was not a problem when theBased on these estimates and tests, the rated power of theshinkansen opened at maximum operating speeds of 210

traction motors was decided, and test cars were built. By

km/h. However, some signs of hunting were seen as wheels

luck and good judgment, the results from the test cars were

became worn so great attention was paid to maintenanceclose to the formula estimates and a rough value of 10 kg/tonof running gear. Running maintenance requires frequent

was used when running at 200 km/h in the open (outside

and troublesome works, so research into preventing hunting

tunnel). When the final trains were completed, the running

continued to enable future speed increases.

resistance was surveyed frequently to improve the accuracyof the formula, including running in tunnels.

Running resistance of high-speed trains
Train resistance is a key factor in determining train

Adhesion coefficient of high-speed trains

performance. It includes running resistance, grade

Adhesion is the fictional grip which transfers acceleration

resistance, curve resistance, and acceleration resistance.

or deceleration force between wheels and rails, and is

But the most fundamental is running resistance on straight,

normally only about 30% in locomotives but is almost 100%flat lines. Running resistance is composed of mechanicalin gears. Consequently, adhesion is an important element inresistance and air resistance, so it is most affected by speed.

locomotive traction.

Air resistance (drag) in particular is nearly proportional to

The planned shinkansen EMU consisted of powered

the square of speed, so the value of running resistance at

cars only with low acceleration and deceleration. As a result,high-speed operations is important in train performance.

adhesion was not thought to be a problem, although the

However, running resistance at speeds above 200 km/h

adhesion coefficient when braking from high speed waswas unknown territory at that time. Since train performance

unknown and caused some concern. It is one of the basic

cannot be designed when running resistance is unknown,

factors for setting train deceleration and determining therealistic estimates were needed. In 1958, the shinkansen

length of deceleration sections in the automatic train control

study group looked at RTRI running resistance tests using

system. However, in the late 1950s, there was little reliable

train mock-ups, investigations by JNR rolling-stock designer

information on the adhesion coefficient at high speeds. The

Shuichi Sawano (1918–) into SNCF’s 1955 test running

RTRI could only find data from overseas for speeds at about

at 331 km/h using electric locomotives each hauling 3

160 km/h, and there were only two or three examples ofcarriages, and results from tests using Odakyu Electric

guesses for the 200 km/h or greater range.
To solve the problem, the RTRI built a full-scale adhesion

Railway’s Type SE EMU.

tester in 1960. A pair of huge rotating wheels were used as

Qualitative trends were found from mock-up tests, but

Japan Railway & Transport Review No. 57 • Mar 201146

Breakthrough in Japanese Railways 7

for 3 kV DC, which was inadequate for longer, heavier trains,
making power collection difficult. A 3 kV DC system would
also suffer large voltage drop, requiring more substations at
closer intervals. Italy runs high-speed trains at 3 kV DC but
is switching to AC and Russia has chosen AC for high-speedlines rather than 3 kV DC.
Electric power for Tokaido Shinkansen is provided by local
power companies, using 50 Hz along approximately 180 kmfrom Tokyo, and 60 Hz for the remaining 370 km. Deliberation
was made as to whether cars should use both 50 Hz and 60
Hz or if power supply in the 50 Hz area should be converted
to 60 Hz. As using both would make the cars heavier andcost more with the technology of the time, the whole line wasunified at 60 Hz taking future increase in the number of trains
Adhesion Tester 

into consideration. For that reason, frequency converters are(RTRI)

installed along the line at the Tokyo side.
Today, rolling stock that uses both 50 Hz and 60 Hz is
designed and produced for use on the Hokuriku Shinkansen.

a substitute for rails. The test data generally showed higher

The Tokaido Shinkansen is still all 60 Hz.

adhesion than actual rolling stock, so researchers believed
it could not be applied to rolling stock design and train

Current collection

operation planning. Therefore, an adhesion coefficient (μ)

Due to the high-voltage feed, the current is lower but even soof 13.6/(V+85) was adopted (where V is train speed) as thea high-speed train can require collection of 1000 A. Images

planned value for prototype shinkansen rolling stock; theof the high-speed test of an electric locomotive in France invalue was halved under wet conditions, taking into account1955 showing large arcing between the overhead contact

conventional test formulas and empirical data.

wire and pantograph suggested that high-speed current

Although the ATC system was based on the adhesion

collection would be a difficult problem.

formula, the high risk of a disaster if the wheels do slide for

Of course Japan at that time had no technology forsome reason resulted in the installation of skid detectors

stable current collection at 200 km/h and the French high-on all axles. Contrary to expectations, the prototypes did

speed tests used a locomotive with only one pantograph,skid frequently on the test track in 1962, so the wheel skid

but one would not be enough for shinkansen EMUs withprotection device was improved for the mass-production

distributed traction. Vibration of a pantograph also affects

cars, and tread cleaners were installed on every wheel.

other pantographs when using multiple pantographs, making

Rust remained on the surface of rails at the start oftechnical issues even more difficult.

shinkansen operations, and skidding frequently occurred.

The basic conditions for stable current collection at high-It took many years before most it was eliminated. Skidding

speed are ensuring that the catenary wave propagation

almost never occurred about ten years later.

velocity is faster than the train velocity as well as having a

Research on adhesion was actively carried out inuniform pantograph uplift spring constant.

development of the next generation of rolling stock as frequent

However, according to theory of the 1960s consideringsliding at the start of shinkansen operation unexpectedly

a mid- to high-speed range up to 200 km/h, speed with nooccurred. The biggest success was in quantifying to acontact loss is, from a pantograph standpoint, found by thecertain extent the relationship between wheel and rail surface

up-down movement vibration theory with the contact wireroughness and adhesion coefficient. The wet state at each

resembling the strings on a stringed instrument. Thinking ofwheel position of long trains was also identified. Thosethe contact wire as springs lined up perpendicularly, speed

successes would be applied from the late 1980s.

with no contact loss is found and calculated from upliftcharacteristics by the pantograph.

High-capacity power supply

As a result, wire contact at faster speeds could be

Long, high-speed trains need a reliable high-capacity power

assured by:supply—a problem that was easily solved by adopting the•

Decreasing the mass of the pantograph, especially•

Increasing the contact wire tension, and making theincreasingly popular AC electrification technology. The feed

the shoe.

voltage was set at 25 kV, which was the global standard atthat time. The early prewar plans for the bullet train called

wire thinner.

47

Japan Railway & Transport Review No. 57 • Mar 2011

•

Minimizing the irregularity of spring constant.

Anti-resonance catenary, modified Y-shaped compound

This theory dominated until the early 1980s and catenary

catenar y, continuous mesh catenar y had complex

wave propagation velocity was not thought to be a problem

structures, and maintenance was difficult, so composite typeat the predominant operating speeds of that time.

compound catenary system was chosen. In this method,

The RTRI started full-scale research in 1955 to develop

the contact wire is slung from dampers which absorb wirea high-speed current collection system. The first tests werevibrations from the pantograph, making it ideal for the multi-

run on the Tokaido main line for the speeds of 95 to 120

pantograph shinkansen EMUs. This was the system devised

km/h, but research started from the end of 1957 on whatby the RTRI.

was at the time super high-speed current collection for the

The initial performance of the composite type compoundshinkansen speeds of 200 to 250 km/h.

catenary was very good, but increasing numbers of

Keeping the catenar y spring constant fixed istrain operations caused wear at the contact wire andimpossible, because the overhead line is supported bydeteriorated dampers, leading to many wire breaks.

poles. However, to keep it as fixed as possible, comparative

Although contradictory to current collection theory, thetests were run on anti-resonance, modified Y-shaped

countermeasure was to strengthen the pantographs. And

compound catenary, continuous mesh catenary, andfrom the 1970s, dampers were eliminated and thicker contact

composite catenary on the Tohoku and Tokaido main lines.

wires were used. This heavy compound catenary had fewer

To decrease pantograph mass, overhead contact line heightwire breaks, but more loss of contact and resultant arcing

was made constant and pantograph vertical motion wascaused more noise along the line. Such contact loss did

decreased. They thus became smaller and lighter. To makenot affect AC-based train operations research continued tothe mass of the collector head in particular smaller, oneeliminate contact loss with major later successes.

pantograph was provided for two motor cars and the power

In pantograph design, the issues facing making themcollection current was reduced. A 16-car train set would

smaller so they are lighter were overcome by fixing overhead

thus have eight pantographs.

contact line height. However, such pantograph design
faced issues with wind-generated irregular lift. Wind against
pantographs when running is strong, and lift acted up anddown irregularly on the collector head and disrupted the

Figure 3 Overhead Catenary Structure

contact force on the contact wire. Wind-tunnel tests led toComposite Catenary Developed for Shinkansen

increase contact force and each new pantograph design iscollectors of various shapes offering slight positive lift tonow subjected to wind-tunnel tests to confirm lift forces.

Traction system
The traction system where the train collects high-voltage AC
power to turn the traction motors was made to be a power
distributed EMU system in line with Hideo Shima’s ideas,

Later Heavy Compound Catenary System

which was accepted unanimously. It was designed to lighten
axle loads and solve adhesion problems and it also offeredstable electrical braking and lowered brake maintenance.
High-speed EMUs designed under that idea were notseen anywhere else in the world back then. At that time,
European high-speed trains running in the 160 km/h range

Figure 4 Pantograph Comparison

For Conventional LineFor Shinkansen
Silicon Rectifier for EMUs 

Japan Railway & Transport Review No. 57 • Mar 201148

(100 Years of JNR Rolling Stock)Breakthrough in Japanese Railways 7

were mostly loco-hauled but after theappearance of the 200 km/h shinkansen,
some European operators increased
operating speeds to 200 km/h and more,
and soon realized the need for lighter axle
loads as roadbeds became damaged.
AC traction systems at that time were
either direct types using AC commutation
motors (mainly low frequency, such as 16.7
Hz) or indirect types with rectifiers and DC
motors. The latter had an advantage for AC
electrification using commercial frequencies

Figure 5 Example Air Pressure Fluctuation Over Time (Lead Car)(mmAq)
100

OutsideIn Airtight Passenger Cabin
62 mmAq

50

7 mmAq0-16 mmAq-50-100

but the large mercury rectifiers used thencould not be mounted easily under the floor-110 mmAq
Entering tunnel
0

Exiting tunnel
5 (sec)of EMUs.
As a result, ef forts were made to
develop a system using commercialfrequency AC-commutator motors withregenerative braking, but that proved extremely difficult.

in places using water such as the toilets and buffets.

As JNR designers and electric manufacturers agonizedOvercoming these problems became a major task. In theover the development, silicon diodes for electric power

end, the whole car body was made airtight. Outside doors

semiconductors appeared. Although many elements had

were sealed by air pressure; airtight diaphragms were

to be connected in series and parallel, under-floor mounting

developed for couplings between cars; and waste water forbecame possible and they were put to practical use onwashrooms and buffets water is passed through a seal (U-dual AC-DC EMUs running on conventional lines in 1960.

shaped pipe holding water at a height of 300 mm or higher)

Shinkansen EMUs were soon equipped with semiconductor

to prevent air flow between the inside and outside.

rectifiers for a system with DC main motors. It proved

And because air starts leaking with aging wear, criteria

incredibly reliable and was used for more than 20 years.

were established for checking air-tightness regularly at

Large volumes of the new electric power semiconductors

maintenance shops to keep it at a certain level.

could be stably supplied thanks to the developmentcooperation of Japanese electric manufacturers.

Continued to JRTR 58.

Passenger cabin air pressure
As tests of prototype shinkansen rolling proceeded at faster
speeds, the problem of in-cabin air pressure emerged.
Air pressure changes greatly as a train enters a tunnel
at high-speed, creating an unpleasant popping feelingin passengers’ ears. The phenomenon had been seen
previously in the single-track tunnels, but its occurrence indouble-track tunnels was unexpected.
Although popping ears is not a major problem for
healthy people, it can be painful for people with colds, etc.,
so a decision was taken to make the car body airtight. The
structure of bodies is complex, and a fundamental change
in terms of design and production technology was needed.
Cars that were strong enough to withstand external airpressure changes were needed, but time was short. For

Asahi Mochizuki

early production cars, areas centring on the passenger

Mr Mochizuki is a Consultant at Japan Railway Rolling Stock &Machinery Association. He joined JNR in 1960, where he was involved
in rolling stock maintenance, and designing EMUs, shinkansen, andelectric rolling stock. Subsequently, he served as a Chief Engineer
Transportation System Division at Toshiba Corporation prior toassuming his current position.

cabin were made airtight and ventilation ducts were closed
when tunnels were detected to secure cabin ventilation.
But making the passenger cabin airtight caused problems
such as poor opening and closing of doors and backflows

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Japan Railway & Transport Review No. 57 • Mar 2011