The Green Paradox of New Energy Vehicles: A System Dynamics Analysis

New energy vehicles produce zero tailpipe emissions and are an effective method for addressing traffic pollution. This study establishes a system dynamics management model to explore the mid- and long-term effects of the new energy vehicle promotion policy on urban traffic and environment. Additionally, we propose a nonlinear function optimization algorithm integrating system dynamics with an optimized even difference grey model to improve the model’s accuracy and validity. The dynamic simulation results show that (1) promoting new energy vehicles reduces tailpipe emissions and alleviates traffic pollution but may lead to a “green paradox” effect in the long term. Positive traffic control measures, such as driving restrictions, accelerate the “substitution effect” of new energy vehicles, and congestion and fuel consumption show a “rebound effect” in later stages. (2) A congestion charging policy reduces vehicle travel attractiveness and alleviates congestion. A sensitivity analysis indicates that a reasonable charging range is 20–40 yuan/(day × vehicle). (3) Introducing congestion charging and improving public transport supply level can effectively weaken the “paradox” effect. This combination not only mitigates congestion and pollution but also reduces economic losses and improves residents’ health. The strategy has a “lag effect” in the early stage but shows effectiveness in the middle (congestion alleviation) and later (pollution control) stages.