As a result of the substantial weight reductions in conventional line vehicles, air resistance has come to represent an increased proportion of running resistance. Measures to reduce air resistance were therefore proposed and have already produced positive results.

      In this study, the reduction of air resistance due to improved vehicle shape was evaluated by a wind tunnel test in which the air flow around the vehicle was reproduced. Using a boundary layer suction device and a mobile ground plate, the flow under the vehicle floor was reproduced (Fig.1), and a method of reproducing the flow over the vehicle roof was proposed by mounting spires upwind of the model (Fig.2).

      The following shows the air resistance reduction from improvement of the vehicle shape of a 10-car commuter electric train.
(1) Under the floor
Considering the underfloor equipment of a conventional line vehicle as a large device, the aspect ratio and position of the device were changed. As a result, the rate of increase/decease reached ±10%.
(2) Head/tail
By streamlining the head/tail of the vehicle from the gable shape, the maximum reduction reached 20% where the maximum length of the improved section was equal to or less than 1/2 of the vehicle width in consideration of securing the car space and doors.
(3) Over the roof
By mounting a simple fairing on the unit coolers of each vehicle (which contribute substantially to air resistance), air resistance was reduced by up to 9%.
(4) Energy saving
A running simulation of a train intended for suburban sections showed that an 11% saving in energy can be achieved by making improvements to the train head and roof (Fig.3).

Fig.1 Wind tunnel test using a mobile ground plate and a boundary layer suction device (large low-noise wind tunnel)

Fig.2 Wind tunnel test simulating flow over the roof (small low-noise wind tunnel)

fig.3 Energy saving effect (improvements to the head and roof)