城市道路路段环境交通容量

将城市环境空气质量控制的思想与城市道路交通容量的概念相结合,提出了城市道路环境交通容量的概念.基于格林希尔治(Greenshields)速度密度的线性模型,得到了速度流量的函数关系;基于机动车排放因子与行驶速度的关系,建立了机动车污染物排放浓度与交通量的关系;运用非线性规划理论,建立了以路段通行能力和污染物浓度控制标准为主要约束条件,以路段交通量最大为目标的最优化模型;运用拉格朗日广义乘子法给出了模型的求解算法.实例研究表明:在控制一氧化碳(CO)浓度下,各车型交通量与在控制二氧化氮(NO2)下的各车型交通量有比较大的差异,特别是微型车、中型车和公交车,造成了环境交通容量要小于道路交通物理容量很多,原因在于不同车型的不同污染物排放因子存在差异.因此,合理的交通结构不仅有利于提高道路交通容量,也有利于保护环境空气质量.

Environmental traffic capacity of link section of urban street

Combining the traffic capacity of urban roads with the air quality control in urban,the paper presents the concept of environmental traffic capacity.On the basis of the Greenshields linear model of speed and density,the function of speed and volume is attained,and the relation between the concentration of pollutants emitted by vehicles and traffic volume is also got based on the relation between the vehicular emission factor and the driving speed of vehicle; The optimal model whose objective is the maximum of traffic volume is developed using the non-linear programming theory,with the main constraints being the traffic capacity and the pollutants' concentration in air quality standard.At the same time,the solution method is presented with the Generalized Lagrange Multipliers method.A case study shows that the traffic volume of different vehicular type under the control of the concentration of carbon monoxide is very different from that under the control of the concentration of nitrogen dioxide,especially mini cars,mid-size vehicles and buses;and consequently,the environmental traffic capacity is much smaller than the physical traffic capacity of road,which is caused by the difference of emission factor of different type of vehicles.So,reasonable traffic structure is beneficial not only to the increase of traffic capacity of road but also to the protection of the air quality in urban.