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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.

From the standpoint of safety, the demands are growing in recent years for better controllability and stability of automobiles and in particular in trucks. The truck, however, when compared with the passenger car, is subject to larger changes in gross vehicle mass and center of gravity depending on its load placement. In addition, since the cornering power generated by the truck tire per load is smaller than that generated by the passenger car tire, it is difficult to introduce significant improvements in controllability and stability simply by use of passive techniques like suspension characteristic tuning. Therefore, studies were performed on the applicability of the 4WS system, an active vehicle dynamic characteristic control technique, to a Truck as a means for solving these problems.

In recent years, with the expansion of highway-networks, the demand for better stability and controllability for trucks is greatly increasing. Therefore, it is necessary to promote speedy development and improved design quality by the use of Computer Aided Engineering (CAE). However, unlike with passenger cars, analysis by simple numerical simulation with less than 10 degrees of freedom is difficult since the torsional characteristic of the chassis frame and large scale deformation of the leaf springs must be considered.