Allison Automatic Transmission Adopted in High-Speed Route Bus in Japan

In late November, 2011, Tohnoh Tetsudou Co., Ltd. (Tohtetsu Bus, headquarters: Tajimi City, Gifu Prefecture) adopted the large “Mitsubishi Fuso Aero Star” route bus, which features an Allison automatic transmission as standard equipment. This was the first adoption in Japan of an automatic transmission bus for use on a high-speed route.

The automatic transmission bus was introduced on a route that connects Nagoya with the city of Kani, a commuter city in that area. Kani is located in Gifu Prefecture and is 30km from Nagoya. The population of Kani began increasing rapidly around 1970 when the town became known as a commuter city of Nagoya, and has grown ever since as the main town for the neighboring area. The bus is used by many Kani residents as a means of commuting, and it provides service to roughly 1,100 passengers each day.


The Kani – Nagoya route covers a distance of 55 km, and over 70% of the route is spent traveling on highways. A long, hilly road (with a maximum grade of 6%) is located on the Chuo Expressway between the Tajimi IC and the Utsutsu Mountain Pass.  When a manual transmission bus travels on this road, the driver must pay close attention while operating the bus in order to minimize the shock to the passengers that is generated from shifting while driving. To overcome this, Tohtetsu Bus introduced three large “Aero Star” route buses from Mitsubishi Fuso in an effort to improve riding comfort and reduce accidents inside the bus.


All Aero Star buses are equipped with an Allison 6-speed automatic transmission with torque converter, so the buses boast advanced driving performance and safety. The Aero Star also features a new engine that was developed in pursuit of combustion efficiency, which exhibits its best performance when combined with an Allison automatic transmission. The torque converter multiplies engine torque while gear changes are made without power interruption.  This results in smooth transfer of power to the drive wheels with maximum efficiency between the engine and transmission.  This allows the bus to blend smoothly into traffic when it makes its way onto a highway or climbs a long, hilly road. The maximum output of the Aero Star is 199kW, which is less than the engine power of a tour bus. However, by adopting a VG turbocharger that exhibits an advanced turbocharging effect from the low speed range, the power that is essential for a route bus is obtained together with good fuel efficiency. Until now, passengers complained about the driving skills of the drivers because of the shock that was generated when shifting gears, but with the introduction of the automatic transmission buses, both riding comfort and safety inside the bus have improved.


Keiichi Sato, Manager of the Kani Office that is in charge of operating this route, commented on the introduction of the automatic transmission buses and gave the new buses high marks. He stated, “The biggest reason for introducing the automatic transmission buses as high-speed buses was to improve riding comfort. If you actually operate the automatic transmission bus, you’ll find that it’s easier to drive because there’s no need to operate a clutch. As a result, driver fatigue is reduced, and we’re able to provide a safe, comfortable ride. I look forward to automatic transmission buses playing an active role in the future as well.”


Naoyuki Miura, a supervisor at the Kani Office, also commented on the anticipated improvements in service and safety and stated, “When you accelerate on a flat road, the Allison automatic transmission automatically shifts up to 6th gear at the same time that the driver presses on the accelerator, and during that time, no shock is generated from shifting, so I expect that the riding comfort of passengers will be further improved. I could tell that the driving performance of the automatic transmission bus is highly predictable.”


Recognizing that public transportation vehicles will continue to play an active role in various situations in the future, Allison Transmission Japan is proud to offer transmission technology that improves safety and make vehicles easier to drive.


About Allison Transmission

Allison Transmission (NYSE: ALSN) is the world’s largest manufacturer of fully automatic transmissions for medium- and heavy-duty commercial vehicles and is a leader in electric hybrid-propulsion systems for city buses. Allison transmissions are used in a variety of applications including refuse, construction, fire, distribution, bus, motorhomes, defense and energy. Founded in 1915, the company is headquartered in Indianapolis, Indiana, USA and employs approximately 2,700 people worldwide. With a market presence in more than 80 countries, Allison has regional headquarters in the Netherlands, China and Brazil with manufacturing facilities in the U.S., Hungary and India. Allison also has approximately 1,400 independent distributor and dealer locations worldwide. For more information, visit