Track
Railway track in the Tōkyō region can be divided into several types:
- Shinkansen Lines
- JR East Commuter Lines
- Other Passenger Lines
- Freight-only Lines
Note: for some commentary on how Japanese railroads superelevate and provide curve easements for track, see my Easements and Superelevation page in the Model Trains section.
Shinkansen Lines
Shinkansen, 新幹線, which translates literally as “new trunk line” are often known in the west as “bullet trains” after the bullet-nosed design, and speed, or the earliest ones. Modern Shinkansen have speeds around 300 kph (180 mph) on the fastest lines. Shinkansen have an impressive safety record. In over 48 years, the single fatality on the system was caused by a door malfunction at a platform, not by an operating train derailment or collision. The only derailment of an in-service train occurred during an earthquake, with no loss of life.
To achieve this, they use a private right of way with no grade crossings, fencing to keep out animals, and often elevated viaduct track (although the latter is more due to scarcity of real-estate, both urban and agricultural). Tracks are also very straight and level, tunneling through Japan’s frequent hills and crossing low areas on fills or viaducts. Track uses standard gauge (1,435 mm or 4’ 8.5”) welded rail, and switches use movable frogs to close the gap normally occurring at the frog.
In newer construction “slab track” is largely used, with rails attached directly to large concrete slabs. The slabs themselves sit on a layer of concrete asphalt, atop an underlying cement structure (such as a viaduct). Slabs have a lot of mass, and are firmly fixed in position using “stopper” posts that stick up through them. This keeps the track rigidly in position and well as providing mass to absorb vibration from moving trains. While slightly more expensive to build than ordinary ballasted track, slab track is low-maintenance and cheaper over the long term.
Ballasted track is also used, although in such applications concrete or synthetic ties, rather than wood, are typical today. Wood was formerly used in switches and open-deck bridges, where its weight and vibration absorbtion were advantages. However synthetic ties made of glass-fiber reinforced polyurethane foam (“Fiber Reinforced Foamed Urethane”, or FFU, branded as “Elson Neo Lumber”) are now being used where the flexibility of wood is preferred, such as on open deck bridges and for switches. These are lighter and longer-lived than wood, and don’t absorb water. They also avoid the ecological issues of creosote-impregnated wood.
While the first line, the Tōkaidō Shinkansen, was built with and is still using (as of 1998) 100% ballasted track, and the Sanyo Shinkansen 95%, later construction largely used slab track, with only 10% ballasted on the Tōhoku Shinkansen.
Recently introduced is “Type D” solid bed track, where concrete ties on a concrete bed are used without ballast. Development on this was started by JNR in the 1970s (and tested on the Tōhoku Shinkansen and Osaka loop line in 1979), but initially the high construction cost was a problem, and adoption of solid-bed track had to wait on an improved design. In the new design, ordinary concrete ties sit in wells in a concrete structure. The ties rest on and are surrounded by vibration-absorbing rubber pads (which can be adjusted to alter rail height) inside a removable polypropylene “hard case” that fits into the well. This was tested (also on the Osaka loop line) in 1997. This method has a significant advantage over slab track in reduction of noise pollution, an important issue in Japan where railway lines run through dense suburban housing areas. It is used today primarily in viaduct track, where it reduces transmission of vibrations to the viaduct structure (and hence noise).
Rail used today is 60 kg/m (121 lb/yd) in 25m (82’) lengths, typically welded into “continuous welded rail” with periodic expansion joints to relieve temperature-induced stresses. The original Shinkansen tracks were laid with 50 kg/m (101 lb) rail. It is attached to ties or slabs with “leaf spring” clips (these look like flat metal plates) with a rubber pad between the rail and tie to help damp vibration.
JR East Commuter Lines
The JR Group of companies was created from the government-owned Japan National Railways (JNR) in 1987, and gradually privatized. In the area around Tōkyō, the JR East company owns and operates most former JNR-track, with the exception of the Tōkaidō Shinkansen operated by JR Central and freight-only tracks owned and operated by JR Freight (JRF also has operating rights over some JR East lines).
Track used on JR East’s narrow-gauge commuter lines is similar in many ways to Shinkansen track, being of 50kg or 60kg rail and often welded. It is mostly ballasted track with concrete ties, although wooden ties appear to still be in use. A track gauge of 1,067 mm (3’ 6”, or “Cape Gauge”) is used. Operating speeds may be as high as 130 kph (80 mph) depending on line and equipment.
JR East uses rail welded into sections about 200m (656’) in length, which they refer to as “long rail”. In part this is for noise reduction (to eliminate wheels clicking over track joints) although it has other benefits for reliability and track maintenance.
To reduce maintenance, JR East developed a low-maintenance form of ballasted track, called the “TC Type Low-Maintenance Track”, in 1997. This uses 400mm (16”) wide concrete ties on 750mm (30”) centers rather than the previously-used 240mm (9.6”) wide concrete ties. This leaves a gap of 350mm between ties, so the appearance is significantly different from ordinary concrete tie track. The ties are placed into a cement filling material within and topped by a conventional ballast structure. The cement is poured on a geotextile material to keep it from penetrating into the ballast. This provides for better load distribution, and well as holding the ties (and rail) more firmly in place, reducing the need to realign track under heavy use. This method of track-laying was introduced on the Yamanote line in 1998 and subsequently expanded to the Keihin-Tōhoku and Chūō Rapid lines. An improved form that can cope with the heavier loads experienced on lines that also handle locomotive-hauled passenger and freight traffic was in development (as of 2005) for use on the Yamanote Freight Line, the Chūō-Sōbu Line, and the Tōkaidō Main Line. A version for use in concrete viaducts was also under development (as of 2005).
In 2002 JR East began deploying new electronically-controlled servo-motor switch machines (“ES-type point machines”) with remote-monitoring capability and began working on a successor (“ESII-type”), the primary benefits of the latter are improved lightning and water resistance and improved grounding to allow them to be used on AC-powered lines. These were placed into service beginning in 2010. Both replaced the older relay-controlled NS-type switch machines. One large advantage of these machines is that they’re structured so that ballast can surround the ties and be tamped by automatic tamping machines, rather than manually. Another is that the ES-type is about one quarter the weight of the NS-type (96kg vs 380kg) making installation and major repairs easier. Operating speed is also roughly twice as fast (3-4 seconds versus 5-6 seconds).
These new switch machines were deployed in conjunction with the “next-generation 2000-type” turnouts. These have an improved design that keeps the point rails more precisely in position, while reducing the probability that points will be fouled by foreign objects. The need for lubrication and adjustment is also reduced. A special “grid type sleeper” system was also created, that replaces the ties under the turnout with a rigid structure, improving the overall stability of the turnout. The first of these was installed in the yard at Omiya Station for testing in 2002. A variation of this for use in cold regions was also developed. This uses a a compressed air line inside the grid sleeper tubes to provide air jets to clear snow from flangeways around the track (snow melting units are also used to prevent moving parts from freezing).
Most JR East track is double-track in the vicinity of Tōkyō, and some lines have two tracks each for local and express (“rapid”) trains. Track centers are typically 3.5m to 4m.
Other Passenger Lines
In addition to the “JR Group” of companies, Japan has a number of private railway companies. These include both public and private corporations, as well as government-backed agencies.
Track for these is not well documented since they don’t operate large R&D organizations that publish papers, but is likely similar to JR East’s, although perhaps making more use of conventional ballasted track, these are more often single-track lines (although many are double-track).
While many use the usual 1,067 mm (3’ 6”) narrow gauge track, different gauges are in use by some of these railways. The Keio Corporation (formerly Keio Electric Railway) operates a mixture of 1,067 mm and Scotch Gauge (1,372 mm or 4’ 6”) lines. Tokyo Metro is also considered a private railway, and it operates a couple of standard-gauge lines (the Ginza and Marunouchi lines) in addition to its 1,067mm network.
In general these companies operate typical commuter and regional inter-city passenger trains at relatively modest speeds. One notable exception is the Keisei Electric Railway Company’s Keisei Narita Line, a new 51 km (32 mi) line connecting Narita Airport to Tōkyō. This uses standard gauge (1,435 mm) track, some of it on concrete slab construction, supporting speeds up to 160 kph (99 mph). The Keisai Raiway converted their other lines from Scotch Gauge to standard gauge in 1959.
The Keikyu Corporation also operates a standard-gauge railway, and its main line into Tōkyō supports speeds up to 120 kph (75 mph)
Freight-only Lines
Freight-only Lines exist both in industrial areas and elsewhere. These are usually single-track, jointed rail on ballast.
References
Development of Low-Maintenance Tracks, Kazuhiko Murao and Hirotaka Aihara, JR East Technical Review, Number 6-Summer 2005.
Development of a New Point Machine for Next-Generation Turnout, Nobuo Obata, Kenji Mori, and Tsunihiro Ichikura, JR East Technical Review, Number 17-Summer 2010.
Development of the Next Generation Turnout for Cold Regions, Kazuhiro Izumi, Yuichiro Hori, and Takahiko Ukai, JR East Technical Review, Number 13-Winter 2009.
Development of Solid-Bed Track with Removable Resilient Ties, Akira Mukai, Katsutoshi Ando, Takahiro Horiike, Youichi Sunaga, Kenichi Takao, Akihito Kito, RTRI presentation at the 2001 World Congress on Railway Research, session 2.1.5 Track Formation and Sleepers.
Describes in detail the structure and development of solid-bed track.
Innovation of Turnout and Switch Machine System, Yuichiro Hori, Kazue Yasuoka, Minoru Obi, Toshiyuki Kaji, Tatsuo Odaka, and Koji Motohasi, JR East Technical Review, Number 2-Summer 2003.
JR East takes measures to create better environment along railway lines, JR East Group Sustainability Report, 2008 (pg 28)
Mentions the use of 200m welded rail segments as a noise abatement measure.
The Mechanism of Railway Tracks, Shigeru Miura, Hideyuki Takai, Masao Uchida and Yasuto Fukada, JRTR Issue 15, March 1998.
A good general overview of Japanese rail track structure, with a focus on Shinkansen design.
Polyurethane Railway Ties in Europe, The Urethane Blog (2008)
Contains a description of the introduction of ties made by Sekisui Chemical of Tōkyō to Europe, with a variety of statistics. The article notes that these have been in use “for 20 years” on Shinkansen lines.
