Comparative cost analysis of electric, hydrogen, and mixed-fleet energy supply modes for a trackless tram line

Trackless trams offer a medium-capacity solution, yet a unified framework for comparing alternative energy modes is lacking. Focusing on the economic dimension of sustainability, this study develops a cost model integrating fixed, operating, and user costs to evaluate battery-electric, hydrogen fuel-cell, and mixed-fleet (a combination of both) modes for trackless trams. Using operational data from Yibin's T2 line, the model quantifies vehicle procurement, energy facilities, driver wages, energy consumption, maintenance, passenger waiting, and in-vehicle time. The results show that the battery-electric mode achieves the lowest daily cost, followed by the mixed-fleet mode, with user costs dominating all modes. Sensitivity analyses indicate that the hydrogen tram procurement cost significantly affects hydrogen-based competitiveness, while extending the facility service life yields limited benefits due to user cost predominance. These findings provide a quantitative basis for energy mode selection, suggesting that reducing passenger time costs may improve system economics more than focusing solely on energy technology advances.