Research and Calculation Method of Road Maintenance Carbon Emission in Expressway Operation Period

In recent years, the greenhouse effect has become a major challenge for sustainable development, with carbon dioxide emissions playing a significant role. In 2022, China’s carbon dioxide emissions reached 12,667,430 tons 1, the highest globally, with the transportation sector contributing about 8% of this, and road transportation accounting for 90% of the sector’s emissions. To promote green development, the Chinese government emphasizes efficient resource use, energy conservation, and emissions reduction, aiming to build a strong transport system by 2035. Understanding carbon emissions in expressway construction is crucial for green development. Studies on highway carbon emissions focus on emissions from road construction and vehicle operation. For example, Chen et al. used a “bottom-up” method to account for emissions during construction, while Tu et al. created a vehicle carbon emission model during operation. With the expanding highway network, maintenance has become essential, but carbon emissions from highway maintenance are often overlooked. Lu et al. divided emissions into material production, transportation, and construction stages, calculating the total emissions from these factors. Yang Yuanyuan et al. divided emissions into six parts and proposed maintenance methods for different conditions. Zheng et al. used a life-cycle approach to assess maintenance carbon emissions and compared methods to identify the least carbon-intensive option. Zhang added congestion and detour emissions to the transportation stage. This paper divides highway construction emissions into four categories: construction machinery, material transportation, construction materials, and recycled materials. It calculates emissions for each stage separately, making the method applicable to all types of expressways. The results of these calculations will contribute to assessing carbon reduction measures in expressway projects.