Purpose: As an ambitious strategy of national interest in China and with an aim at achieving the ‘one-hour economic circle’ among Greater Bay Area cities by 2035, the Guangdong-Hong Kong-Macao Greater Bay Area has been transformed into a world-class bay economic belt in South China. Consequently, the large-scale construction of transportation infrastructure inevitably resulted in the consumption of a lot of resources and significant environmental impact. Such a scenario could produce conflicts with Greater Bay Area’s commitment on the sustainable development goal, such as China’ carbon intensity reduction. Methods: In this study, the environmental impacts caused by highway pavement in Greater Bay Area at urban agglomeration level were quantified through life cycle assessment method, measured by greenhouse gas emissions (CO2eq). Results and discussion: Our results show that the total emissions resulted from the use of materials during the construction of highway pavement, its maintenance, and rehabilitation phases in Greater Bay Area reached 4.4 (± 0.25) million tonnes CO2eq in 2018, of which material phase (material production and transportation to the construction site) accounted for more than 70% of the total impact. The construction phase of asphalt pavement is larger than the maintenance and rehabilitation phase, while the maintenance and rehabilitation phase of cement concrete pavement is larger than the construction phase. Moreover, a scenario-based analysis implies that the continuing growth of highway mileage in Greater Bay Area will accelerate the environmental impact till 2035. Conclusions: These findings can help understand the impacts of highway pavement in Greater Bay Area and provide useful support for policy-makers. In addition, the methods are useful for the quantification of greenhouse gas emissions of highway construction on city level in China and beyond.