Role of new energy vehicles in expressway decarbonization: Evidence from Guangdong, China

Decarbonizing expressways, a major source of transport emissions, is critical for climate goals. However, quantifying the impact of new energy vehicles (NEVs) remains a policy challenge, as standard models often fail to capture local conditions, leading to uncertainty in policy evaluation. This study addresses this gap using a dual-model framework, with Guangdong, China, as a case study. First, we developed an expressway localized COPERT model (EL-COPERT) that corrects baseline fuel estimates (18.5% for passenger vehicles, 5% for trucks). The model's high accuracy was validated using real-world field data and microscopic traffic simulations (MAPE <0.085). Second, a system dynamics-based expressway carbon emission model (ECM) projects carbon trends to 2035 under various scenarios. The baseline scenario shows a 14.7% emission reduction from NEVs by 2035, with transportation structural adjustments adding 2.4%. Crucially, our analysis reveals this baseline is insufficient for peaking. Accelerated NEVs deployment, combined with technological innovation, is essential to achieve an emissions inflection point around 2031. This research provides a validated framework, quantifying baseline scenario limits and supporting the strategic planning required to accelerate the transport sector's low-carbon transition.