Analysis of Energy-efficient Operation Characteristics of Express Trains using Global Navigation Satellite System Data

Abstract: To reduce railway energy consumption, optimizing driving techniques is an effective approach, along with enhancing energy-efficient rolling stock and infrastructure. To identify operation characteristics associated with lower energy consumption and to investigate the relationship between driving speeds and energy consumption, this study analyzes operation performance data.Data were gathered over one year from GNSS-equipped tablets. Analysis focused on one segment between two scheduled stops of the same limited express train. After excluding data reflecting deceleration due to signal aspects or departure delays of ≥1 min, 95 out of 331 data points were used. Excluding outliers, two groups were formed based on estimated energy consumption: the lowest 25% classified as the "low group" and the highest 25% as the "high group." Energy consumption was estimated using GNSS data by considering running resistance and track gradient. T-tests were conducted to assess significant differences between the two groups for mean estimated energy consumption, travel time, and driving speeds at three locations: (1) before the speed restriction zone in a downhill section, (2) before the speed restriction zone in a flat section, and (3) before the station stop. The locations chosen for comparing driving speeds were characterized by remarkable speed variability, situated before the speed restriction zones and the station stop requiring deceleration. This was based on the premise that shortening acceleration time and lower speeds prior to braking generally enhance energy efficiency and greater speed variability may reflect differences arising from driving techniques.T-test results indicated that the mean estimated energy consumption of the "low group" (136.1 kWh) was significantly lower than that of the "high group" (150.0 kWh). By contrast, the mean travel time of the "low group" was significantly longer (low: 13 min 34 s, high: 13 min 3 s). Regarding driving speeds at the locations, the "low group" displayed significantly lower speeds: (1) before the speed restriction zone in a downhill section (low: 102.2 km/h, high: 108.5 km/h); (2) before the speed restriction zone in a flat section (low: 114.5 km/h, high: 120.9 km/h); and (3) before the station stop (low: 111.0 km/h, high: 122.2 km/h). The reduced speeds prior to the onset of braking during low-energy-consumption runs corroborated theoretical expectations. Despite the "low group" having a longer mean travel time, it remained within the scheduled travel time (13 min 45 s). Regarding energy-efficient operation characteristics, the "low group" exhibited greater variability in driving speeds at locations (2) before the speed restriction zone in a flat section and (3) before the station stop. Accordingly, train performance graphs illustrating driving speed versus travel distance for the "low group" were examined. Two energy-efficient operation patterns emerged: (A) increasing speed during the midsection and coasting after the speed restriction zone before the station stop and (B) coasting during the midsection and accelerating after the speed restriction zone before the station stop. Pattern A was frequently observed among train drivers who were conscious of energy-saving practices. Interviews with train drivers indicated that pattern B was favored to prevent deceleration caused by signal aspects.

Keywords: Energy-efficient train operation, GNSS data analysis, Train operation characteristics

DOI: 10.54941/ahfe1007017

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