Failure Knowledge Database / 100 Selected Cases

Train Fire at Sakuragi-choApril 24, 1951 at the Sakuragi-cho Station on the Keihin-Tohoku line
Masayuki Nakao (Institute of Engineering Innovation, School of Engineering, The University of Tokyo)
A disastrous train fire occurred at the Sakuragi-cho Station on the Keihin-Tohoku line when a MOHA-63 train
touched a sagging overhead wire and sparks caused a fire, killing 106 and injuring 92 passengers trapped in therailcars. Although the direct cause of the train fire was a s tringing construction accident, heavy casualties weredue to the train operators’ inadvertent control input. The passengers were trapped inside the railcars because theoperators deactivated the pantograph, locking al l do ors, and the win dow str uctures di d not p ermit e vacuation(the middle panel of the three-panel window was fixed to the frame). Photo 1 is the press photo of the accident.

Photo 1. MOHA-63 in Flames (Mainichi Newspapers) [2]
1. Event
Near the Sakuragi-cho Station on the Keihin-Tohoku line, the first car of a 5-car MOHA-63 train touched asagging overhead wire and sparks caused a f ire, k illing 1 06 and injuring 92 passengers tr apped in t herailcars. The fire destroyed the first car completely and the second car partially. The heavy casualties weredue to the closed d oors and the particular window s tructures in which the middle panel of the three-panel
window was fixed to the frame (Photo 2).

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Failure Knowledge Database / 100 Selected Cases

Photo 2. MOHA-63 Train [2]2. Course
Figure 1 s hows the map of Sak uragi-cho at th e tim e. C onstruction cr ew was replacing i nsulators ofoverhead wires at the Sak uragi-cho Station. At ar ound 13:38, on e of the construction crew hit th e beamwith his/her spanner wrench by mistake, cutting a ha nging wire at the circulatory shunt. As the result, thecontact wire forthe i nbound line hung down. (Hanging wir es s upport electrical wir es. Th e tr ain’s

pantograph makes contacts with the contact wire.)
A 5-car MOHA-63 train 1271B outb ound for Sakuragi-cho left the Yokohama Station with a nine-minutedelay. It was approaching its last stop, the Sakuragi-cho Station.
At around 13:42, the 1271B attempted to change its line from outbound to inbound at the 5 0m point fromthe Sakuragi-cho Station when the c ontact wire got tangled up with the pantograph of the first MOHA-63
car. The frigh tened t rain operators lo wered the pan tograph, but it topples s ideways touching the r ailcar.
Sparks started a fire on the wooden roof and spread to the entire car.
Two transformer s ubstations, Yokohama and Tsurumi, were feeding electricity to the overhead wire at theSakuragi-cho Station. The electrical current breaker was promptly activated at the Yokohama Transformer
Substation, but not at the Tsurumi Transformer Substation. The Tsurumi Transformer Substation continued
feeding 1,500V of electricity for about 5 minutes.
The first car was carrying more than 150 passengers and they attempted to escape from the fire. They wereunable to open the automatic doors to outside. They attempted to escape to the second car, but the throughpassage door did not open. Opening of the window was too small. The passengers were literally all trapped
inside the railcars waiting to be burned.
The train operators who saw fire attempted to detach the first and the second cars from the rest.
The fire completely d estroyed the first car in about 10 minutes and par tially d estroyed the s econd car ,killing 106 and injuring 92 people.

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Failure Knowledge Database / 100 Selected Cases

Figure 1. Old Sakuragi-cho Map [2]3. Cause(1) Stringing construction accident
This is the dire ct cause of the train fire . C onsidering that re placement of insula tors i s a re gular
maintenance task, t his sort of acci dent co uld happen any time. Th e m aintenance crew should havegiven a re d fl ag s ignal a nd s topped th e n ext t rain, but th e ot her c auses, ra ther t han the s tringing
construction accident, multiplied the damage to the accident.
(2) The electrical current breaker did not function at the Tsurumi Transformer Substation.
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Failure Knowledge Database / 100 Selected Cases(3) Structural issues of the train modela.

The middle panel of the three-panel window was fixed to the frame (each panel was only 29 cmhigh). Opening of the window was too small for a person to go through (Figure 2).

b. There was no sign indicating how to open doors in an emergency.
c.

Through pass age do ors to adjoinin g cars open inward. Thedoorway was too c rowded withpassengers for any of them to open the door inward (Figure 3).
d. The model w as pr oduced during or r ight after the war , and i t w as a combustible pr oduct withminimum installation of safety devices and with flammable-painted plywood roof.
(4) The train operators and crew did not manually open doors to let the passengers off the railcars.

Figure 2. Three-Panel Window Structure of MOHA-63

Figure 3. MOHA-63 Doors
The train operators attempted to detach the first and the second cars from the rest as trained when theyassessed that the fire was not extinguishable. However, one can hardly believe that their action is basedon reasoned judgment and lifesaving.
4. Immediate Action
In order to an alyze t he a ccident causes, J apanese Na tional R ailways ( current Japan Railway s) conducted
4Failure Knowledge Database / 100 Selected Cases
fire experiment at then Toyokawa Branch Factory. In less than two months after the accident, the Railway
Safety and Inspection B ureau of the M inistry of Transport pu blished the in vestigation report. T he report
described th at the structure a nd the s afety fea tures of th e MOHA model was neither fir e-resistant norprepared for fir es. Al l r ailcars produced dur ing th e war wer e impr oved by coating of railcars with
fire-retarding paint, better insulation of collector, and provision of a through passage to adjoining cars forevacuation.
5. Countermeasure(1) Window structures to permit evacuation. Three- panel windows were c hanged to two-panel windows.
JNR train mo dels abor ted three-panel wi ndows af ter the Sakuragi-cho ac cident. F or all MOH A-63
trains in service, the middle panels of the three-panel window were modified to be movable.
(2) Signs in dicating ho w to o pen do ors in an e mergency. The em ergency handle lo cations und er thepassenger seat were indicated b y red pa int an d sig ns “In ca se of em ergency, u se this handle tomanually open the door” were installed.
(3) Provision of a through passage to adjoining cars.
(4) Better insulation of pantograph and roof.
(5) Fire-retarding coating to improve fire-resistance.
(6) Mechanisms permitting rapid power shutdown in case of abnormal current flow.
6. Summary
The MOHA-63 model was developed aiming at the maximum capacity for a smaller railcar area in wartime
years. The three-panel window was developed to air the packed railcars and make passengers including thestanding in aisles as comfortable as possible. The window had a fixed middle panel, and the to p and thebottom panels s lid open f or ven tilation. The us e of natural v entilation and sus tainable ener gy are more
economical than fo rced ventilation an d seems a brilli ant id ea, but this p articular window structure
compromised safety of the passengers.
7. Knowledge(1) A small accident may lead to a disaster.
(2) Improvement in performance and efficiency may compromise the safety.
(3) Designers and developers must ascertain the safety of the resulting product when implementing a newstructure. They must test the safety under various hypothetical emergency situations.
(4) Instruction manuals and rules do not work in some circumstances. They may produce a fatal mistake.
(5) Passengers may want to be prepared and check evacuationroutes whentraveling by pu blictransportation. Passengers must remain calm in emergency circumstances to minimize the accident.
8. Background5

Failure Knowledge Database / 100 Selected Cases
The MOHA-63 model was a commuter railcar produced more than 1,000 during and after the war. It was inservice on the JNR lines as we ll as on private railway lines as JNR transferred railcars to he lp the private
sector during the postwar years of recovery. The MOHA-63 model was design to carry as many passengers
as possible in a railcar and it h ad t he reduced nu mber of se ats. The nu mber of doors was incr eased to 4
from the av erage of 2 – 3 per a railcar to quick ly load and unload pass engers. Due to the war time andpost-war shortage in production material, some key devices were dropped or substituted by inferior ones.
Its de sign and production traded in q uality for quantity, di sregarding th e s afety. In response to theSakuragi-cho accident, the model number was changed to MOHA-72 after various improvements including
fireproofing were made. Considering the fact that the improved model was in service until recently and thecurrent commuter rail cars h ave 4 doors for it s 20m-length body , the 4-door body must h ave b een an
appropriate design. For railcar windows, while the three-panel window was inappropriate for safety reasons,more railcars have fixed s ash windows in recent y ears as air co nditioners beca me popular and large-size
glass became more reasonable in price. This may be due to vast improvement brought in fireproofing andfire-resistance design over the years.
References[1] “Nihon-no Ressha Kasai Taisaku-wa Banzen-ka? (Does Japan Have Effective Train Fire Control Policy?),
Pail and Rapid Transit Mechanical Engineering (Nagase Laboratory), Kanazawa Institute of Technology,
http://www2.kanazawa-it.ac.jp/knl/nagase/comment19.html[2] Yasutomi Sasaki, Ryoichi Amiya (1995) Zoku Jiko-no Tetsudooshi (History of Train Accidents II), Nihon
Keizai Hyoron, LTD.
[3] “Hokusoo Yawa (Northern Sobu Nights)”, http://www.ne.jp/asahi/hokuso2/hokuso2/html-yama-03.html[4] “Kako-no Omo-na Kasai Jiko (Major Fire Accidents in the Past)”,http://www1.odn.ne.jp aaa81350/kaisetu/kasai/jikorei.html

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