Freight trains are usually more about predictability than speed. Unless you’re transporting food or mail, duration normally doesn’t matter. However, Japan’s high-speed narrow-gauge passenger services make operating express freight easier, and the right-of-way is already designed for higher speeds, so the cost doesn’t need to be justified by freight use, and having trains run at a similar speed to passenger services makes the two work together better.
Some of these express trains follow a set route and schedule, using dedicated equipment, and are often operated on behalf of one company (which may be an industry, or an express shipping company). That’s true of many non-express unit freight trains also.
Additional information on containers used for freight transport can be found on the Freight Containers page, and details of the typical flatcars used for containers can be found in the KOKI entry on the Freight Cars page.
Express Freight Train Services
High speed freight trains today are divided into three classes (Japanese wikipedia): class A, rated for 100 or 110 kph but also including the M250, class B rated for 95 kph which includes both container trains and tank trains using the TAKI 1000, and class C rated for 85 kph. There are two lower classes of ordinary “dedicated” freight train (Japanese wikipedia): class A (yes, they reuse the letters), rated for 75 kph and class B rated for 65 kph, although it sounds like the last one is fairly rare now.
Express freight appear to operate on a daily basis to/from larger freight stations.
Some of these trains even have names. I know of the following named express freight services, there are likely others.
This was an express carrying refrigerated 20-foot containers between Hokkaido and Tōkyō. It used 50000 and 57000 series KOKI cars and UF26A refrigerated containers, plus a separate generator container (the UF26A had cooling equipment but needed an external power supply). The generator was at one time the ZG-3, although there is also reference to a ZG-1 (unclear if it was for an earlier version of this train, or another). I’ve seen one reference to this as the “JR Cool Express” (and a photo of a container flat lettered “COOL EXPRESS” in roman letters) plus another reference to it being operated for Nippon Express. The use of these older cars probably limited it to 85 kph operation.
The UF26A (20-foot) probably wasn’t the only container used, as the description of the UF15A (12-foot) container notes that it had a 1000 series form powered by the ZG-3 generator container also. The Japanese wikipedia page for the UF15A container notes that use of centralized power for refrigeration is no longer practiced, so that form of the train clearly no longer exists.
The M250 Super Rail Cargo train is Japan’s only freight EMU (electric multi-unit) train. The equipment it uses comprises a set of purpose-built power cars (two at each end) and twelve more container flat cars, carrying specialty 30-foot domestic containers. This is used, since 2004, on a high-speed overnight freight, the Sagawa Express, from Tōkyō to Ajikawaguchi Station in Osaka. The trip takes 6 hours and 10 minutes each way, for an average speed of 91 kph (57 mph). Each set of 16 semi-permanently-coupled cars includes four motor cars (two at each end) that can carry a single 31-foot U54A container, plus twelve flatbed cars that can carry two. At the Tōkyō end, the train terminates at the Tōkyō Freight Terminal, located adjacent to the Oi Rail Yard (Shinkansen maintenance facility) on an artificial island just north of Haneda airport and convenient to container-ship facilities located on the island).
The four power cars produce 3,520 kW (4,720 hp) and can pull a sixteen-car train at speeds up to 130 kph (81 mph), making it Japan’s fasted freight train (until the introduction of Shinkansen freight through the Seikan tunnel to Hokkaido) and one of the fastest narrow-gauge trains.
There are (apparently) two sets of trailers, and three sets of motor cars (presumably the third set is to allow maintenance without disrupting train operations).
Note: the “express” in this name is the Kanji for “courier” (“急便” or “Kyūbin”) and appears to be the company name of the express company, and may not refer to the train (except for it being a train “of Sagawa Express”).
Toyota Longpass Express
The Toyota Longpass Express (Japanese Wikipedia) is a 100 kph unit container train that runs daily between Morioka Terminal Station in Iwate (in northern Japan) and Nagoya South Freight Station in Aichi (in western Japan); a trip of 15-20 hours. In the Tōkyō region it uses the Tōkaidō line via Shin Tsurumi station to the Musachino line to Omiya yard via the Utsunomiya line.
This is a twenty-car train using specialty U55A containers, a 30-foot domestic design, with up to two per car.
Note: the “express” in this name is the English word rendered phonetically in Japanese katakana (“エクスプレス” or “ekusupuresu”).