Evaluation of external costs in road transport under the openness of a gated community

Residential quarters in Chinese cities are usually walled off from their surrounding roads for security purposes.Recently,the Chinese government has decided to thoroughly open gated residential communities in order to improve traffic capacity and coordinate major roads in the road network,which will inevitably pose challenges,such as environmental pollution,for community members.Unfortunately,before this decision,there were no comprehensive investigations into whether this measure works for road traffic or how much the adverse impact exerts upon residents.Here,we propose a comprehensive method combining microscopic traffic simulation with a vehicle exhaust emission and dispersion model and a noise emission and attenuation model,in addition to a consideration of social cost,to evaluate the possible influence of opening an enclosed residential community to surrounding roads.The validity of the hybrid model was assessed by an assumptive case of two rectangular gated communities under varying traffic flow and five community opening modes.Preliminary results indicate that the opened community outperforms the gated in the most of 49 percent reduction in comprehensive cost.A more detailed analysis reveals that the appropriate extent of openness should rely on the actual situation,and potentially serves as a foundation for the healthy development of communities and cities.Based on the case study results,this paper outlines some strategical suggestions for improving enclosed residential areas by striking a better balance between traffic capacity and environmental risks.