magnetic synchronous motors, can reduce energy loss during transmission. Regenerative braking improves the recovery and reuse of braking energy to the maximum extent and is the preferred approach for saving energy. Figure 5 shows the energy flow diagram for regenerative braking. Optimal Energy Utilization in High-Speed Train Operations Current research on energy utilization optimization for high-speed trains focuses mainly on two procedures. The first reduces the energy consumption under given operating conditions with specific technical constraints, Energy Fed in at Electric Substation Catenary Losses and the second improves the driver's handling capabilities by adopting energy-saving operational strategies. Table 5 depicts methods for energy saving and emission reduction. To maximize the energy efficiency of trains with respect to energy flows and energy consumption characteristics, the contribution rates of various energy-saving measures for high-speed trains are shown in Figure 6. According to the pie chart distribution, energy recovery and energy-saving operation are the two most efficient energy-saving measures. Moreover, once the running route and operational scheme of high-speed trains are determined, optimizing the driver control strategy and Losses in Traction System Comfort Functions Air Resistance and Friction Train Net Energy Intake Mechanical Energy at the Wheels (Train Motion) Inertia and Grade Resistance Regenerative Braking Energy Returned Catenary Energy Recovery Unit Dissipated in Brakes Losses in Traction System Figure 5. The energy flow diagrams for passenger trains with regenerative braking. TABLE 5. A summary of energy saving and consumption reduction of trains. (Source: New Lines Programme.) Measure Types Ways Impact on Energy Consumption Technology Aerodynamics and friction Shinkansen air resistance is reduced by 10%, which can reduce 6% of carbon dioxide emissions. Reduce the loss-of-traction The overall energy consumption can be reduced by 1% when reducing the energy system consumption of traction components by 1%. Operation Regenerative braking This can save 8-9% in energy consumption. Improve space utilization A Train à Grande Vitesse double-decker design reduces energy consumption by 30% compared to single-layer designed seats per kilometer. Improve passenger service function efficiency Reducing 6% of passenger climate control energy consumption can reduce the overall energy consumption of trains by 1%. Effective traction strategy A 7.5% increase in traction efficiency is seen. Load factor Of all the measures, this method has the greatest potential to reduce passenger per kilometer of energy consumption. IEEE Electrific ation Magazine / S EP T EM BE R 2 0 1 9 71