Relationships between vehicle kilometers traveled and carbon emissions based on urban size

Urban development patterns influence the increase or decrease in Vehicle Kilometers Traveled (VKT), which subsequently affects carbon emissions. Previous studies have established a direct correlation between VKT and carbon emissions; however, according to the Environmental Kuznets Curve, this relationship may vary depending on urban size. This study examines the relationship between VKT and carbon emissions, exploring the three-dimensional impact of urban size on this dynamic. To achieve this, threshold regression model and multilevel model were employed. The findings reveal a threshold range in which urban size moderates the relationship between VKT and carbon emissions. Furthermore, while an increase in VKT leads to higher carbon emissions as urban size grows, the effect diminishes beyond a certain threshold. This study builds upon the Environmental Kuznets Curve framework and emphasizes the importance of VKT reduction as a key factor in mitigating carbon emissions, while suggesting that spatial planning strategies should be tailored according to urban size.