Integrated simulation and optimization approach for studying urban transportation-environment systems in Beijing

Based on a systematic analysis of Beijing's Urban Transportation-Environment Systems (UTES), an integrated model is built, seeking an optimized and feasible trip mode structure on the premise of resident trip demands, environmental and resource capacity, and feasibility of policy adjustment in Beijing. First, a system dynamics model and a linear optimization model are founded for the Business-as-Usual simulation and best results of transportation development. Next, eight ameliorated scenarios combining four policies on Clean Transportation, Bus Priority, Subway Priority, and Car Trip Restriction are re-simulated. Finally, the results from nine scenarios are compared with the optimized results through grey correlation assessment. Findings show that adjustment policies have positive effects on the improvement of UTES, although these are varied and occur at different time scales. Integrated adjustment measures for sustainable transportation should be employed in Beijing because a combination of policies yields better effects than individual regulations. The derived optimized trip mode structures of Beijing in 2020 for subways, taxis, cars, buses and bicycling or walking are 19.41, 2.58, 24.99, 32.57 and 20.46% respectively, while daily resident trips reach 59.5 million. In this scenario, the environmental and land use demand are within supply capacity, whereas energy supply remains limited.