To reduce car manufacturing costs, a relatively old commuter diesel train was completely renovated to produce the sightseeing train. The cars were painted black on the landward side and white on the seaward side, giving them a striking appearance. Moreover, to enhance the viewing pleasure of passengers, some of the seats facing the windows on the seaward side of the car are reclinable. Teak or cedar is used for the interiors to create a relaxed and bright atmosphere. Bookcases containing various types of works for passenger use have been built along one side of the car. As just described, this train has become an attraction in itself because of its characteristic interior and striking appearance.

This limited express service runs along a section with large track irregularities because of its relatively low level of maintenance criteria compared with those of other sections. This increases vertical vibration of the car body, particularly within the 1-2 Hz frequency range which may result in reduced ride comfort. A secondary suspension damping control system using variable vertical hydraulic oil dampers was therefore developed which can significantly cut this vertical vibration.

Each car is equipped with four dampers, a controller, and four accelerometers. Variable vertical dampers are mounted parallel to the secondary coil springs replacing the original passive vertical dampers. The direction of the damping force generated by the variable vertical damper can be controlled by the command current alone, eliminating the need to consider the piston stroke velocity of the damper from the point of view of the controller. The control algorithm which controls variable dampers is based on the sky-hook control theory.

In addition to the above mentioned functions necessary for controlling the dampers, the controller is also equipped with functions to detect broken wires, accelerometer faults and damping force of the dampers. The fault detection method developed for the damping force involves separating the vertical vibration acceleration of the car body, which is used to control the damper, into bouncing and pitching components of the car body then examining the changes in the phase difference between the two components. When a fault is detected, damper control is automatically stopped as part of a fail-safe mechanism.

Vehicle running tests were carried out before commercial operation of this train on a local commercial line. The results demonstrated that the system can reduce the power spectral density peak value of vertical vibration acceleration in the rigid body mode by approximately 80%. This system suppressed vibration to a degree which passengers would be able to perceive.

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