Emission analysis of multi-mode public transportation based on joint choice model considering built environment factors

Urban public transportation is crucial for achieving low-carbon cities but faces challenges due to urban planning and transportation coordination issues. This study introduces a joint decision model for multiple public transportation options, grounded in the cross-nested logit (CNL) framework, integrating departure time and travel mode dimensions. It combines three key variables—travel scheme, built environment, and carbon emissions—to assess transportation choices comprehensively. CO2 emissions are evaluated with the COPERT (COmputer Programme to calculate Emissions from Road Transport) model for accurate environmental impact assessments. Utilizing multi-source data from Shenzhen, including smart card, vehicle trajectory, and order data, the study evaluates factors influencing public transportation choices and compares emission reduction potentials. Results indicate that Shenzhen travelers are more sensitive to traffic and built environment service levels when choosing departure times rather than travel modes. The findings highlight the significant role of metros and shared bicycles in reducing emissions and suggest built environment adjustments to promote these low-carbon travel modes. Additionally, elasticity analysis and Monte Carlo simulations provide insights into future strategies under different emission reduction scenarios. These findings offer a theoretical basis and practical guidance for improving transportation structure and built environment, supporting the development of sustainable and low-carbon cities.