The Law Concerning the Rational Use of Energy (a.k.a. the Energy Saving Law) has been revised to require railway operators with 300 diesel vehicles or over to promote environmental preservation measures such as introducing low fuel-consumption cars, and reporting amounts of energy consumption and CO₂ emission on a regular basis.

When energy saving was discussed in the past, the amounts of energy consumed by vehicles under different conditions of operation were not known unless the vehicles ran on actual tracks. To address this, the RTRI developed a calculation system to enable estimation of the volumes of fuel consumed and CO₂ emitted in running with data obtained using software to draw train performance curves and engine performance data showing the characteristics of fuel consumption (Fig. 1).

This system has a function to display the results of calculation and draw graphs to show changes in the volume of fuel consumption over time (Fig. 2). The RTRI measured the volume of fuel consumption and the like in running tests and compared the measured and calculated values to verify the validity of the system. In a case where a vehicle ran for about 29 minutes (including a powering time of 16 minutes), the measured volume of fuel consumption was 19.3 L, while the system gave a calculated value of 21.8 L, suggesting that agreement holds roughly between the measured and calculated values. This system can be utilized for discussing energy-saving measures including the reduction of fuel consumption, and designing environmentally-friendly rolling stock like being free from exhaust gases (Table 1).