Abstract for: Decarbonizing German Heavy-Duty Transport: A Scenario-Based Study of Hydrogen Truck Fleet Evolution

Decarbonizing heavy-duty transport is essential for European climate neutrality by 2050, yet the transition pathway for hydrogen-powered trucks in Germany remains uncertain due to nonlinear feedbacks among policy, infrastructure, and total cost of ownership. This study analyzed Germany's heavy-duty vehicle fleet (2020-2050), focusing on hydrogen diffusion. Using System Dynamics in Stella Architect with Bass diffusion, it modeled competition among diesel, BEVs, and FCEVs via attractiveness-based adoption, HRS expansion, and dynamic CAPEX learning. Calibrated to 2020-2025 data, results showed ~535,000 diesel trucks, 10,597 BEVs, and 188 FCEVs. Baseline projections showed fossil-fuel decline, BEVs emerging as primary successor by 2049, and hydrogen remaining niche without external acceleration. Scenario analysis showed increasing policy-driven innovation disproportionately accelerates early uptake, but long-term diffusion depends most on hydrogen fuel costs: with initial 11 EUR/kg and decay d=0.03 toward ~5 EUR/kg by 2050, baseline yields ~10,000 hydrogen trucks, while doubling price reduction produces >25,000. Infrastructure streamlining (reduced bureaucracy and construction time) moderately increases the 2050 hydrogen fleet (~9,000 to ~12,000). Meeting targets necessitates a strategic transition from relying primarily on upfront subsidies toward implementing reductions in operational costs. At the same time, it is crucial to ensure that adequate coverage of HRS is maintained. Such coverage plays a vital role in fostering a self-reinforcing diffusion process. Balancing cost reductions with sufficient HRS coverage ensures that operational efficiencies do not compromise the support structures necessary for sustained growth and widespread uptake, ultimately enabling the achievement of long-term targets. proofreading the manuscript, improve language and grammar