This paper deals with the superb hybrid-electric vehicle to be put to use as a super-low-floor city bus - a highly efficient vehicle which can offer both excellent fuel economy and low emissions of exhaust gas. In order that oil resources may be put to more effective use, the research and development activities described herein aimed at realizing a vehicle with lower energy consumption, higher efficiency, lower fuel consumption, and also cleaner exhaust gasses than those of diesel-engine busses which are traditionally used in urban environments. A series-type implementation was adopted for the hybrid electrical-drive system in order that a higher degree of energy efficiency could be achieved. Furthermore, the newly-developed high-performance lithium ion batteries were adopted for use in this vehicle. In addition to this, the use of super-wide, single tires in combination with the hybrid system permitted a high degree of flexibility in the arrangement of mechanical components; consequently, the width of the rear pathway could be increased to 1.4 times the conventional size. And as a result of this modification, it was possible to realize an epoch-making stepless bus with a wide, low floor. Furthermore, this development project was also successful in the creation of a more-welcoming, new-generation HEV bus system which removes barriers to usage by wheelchair-confined persons and all other types of passenger.
The next step in this project involved the analysis of fuel-efficiency and exhaust-gas characteristics. The results of these activities showed that, in comparison to manual-transmission vehicles running on regular diesel fuel, fuel consumption levels were reduced by approximately 33%; and when compared with automatic-transmission vehicles, the level of improvement increased to approximately 40%. Furthermore, it was also learned that levels of exhaust-gas emission (specifically, NOx) were reduced by 50 to 70%, thus confirming the highly-efficient and highly-clean nature of the bus in question.