Research On Atmospheric Envirionmental Carrying Capacity Of Urban Road Traffic

With the progress of urbanization, the great increase of travel demand in urban area brings negative effect on environment and leads to the deterioration of environment, and the traffic system has become the main source contributing to the urban environment pollution. Under that condition this paper researches on the constraint that the traffic environment puts on the development of traffic system and the maximal development scale and intensity of traffic system under the limit of environmental capacity, to realize the benign operation of environment system and traffic sustainable development.Firstly this paper discusses the basic theory of urban traffic environmental capacity and carrying capacity, then carryies quantitative research on urban traffic atmospheric environmental capacity. Based on modified singal box model, the model for urban traffic atmospheric environmental capacity is developed. Especially, for different kind of atmospheric pollutants, different mathematical models are developed.Then, this paper does further research on atmospheric environmental carrying capacity of urban road traffic from the macro level and meso level respectively. At the macro research of traffic atmospheric environmental carrying capacity, the mathematical model is developed based on singal box model of atmospheric environmental capacity to forecast the maximal owned quantity of motor vehicle within the urban area. The result could serve as a basis for controlling the maximal quantity of motor vehicle and making traffic policy.The meso research on atmospheric environmental carrying capacity of urban road traffic is the key of the paper. This paper for the first time proposes the idea that takes traffic flow to quantitively measure the meso-level traffic environmental carrying capacity, and divides the model construting process into two steps. The first step is to build the mathematical relationship between emission intensity and pollutant concentration, and the second step is to establish the mathematical relationship between emission intensity and traffic flow. During the first step, the relationship between emission intensity and pollutant concentration is built based on the modified emission optimization model; during the second step, after analyzing the relationship between emission intensity and traffic flow, this paper adopts the road traffic flow as intermediate variable to construct the model describing mathematical relationship between emission intensity and traffic flow. At last, considering that there are always some differences between the actual situation and the model assumptions and those differences could have large effect on the actual maximal permitted value of traffic flow, this paper makes some adjustments and modifications to the traffic flow value under the ideal situation. The forecasting results could be used to check whether the results of traffic assignment on road network exceed the limit of environmental carrying capacity, and provide reference for regulating assignment of traffic flow to meet the environmental quality standards.At last, this paper takes Chengdu as a case study and predicts the atmospheric environmental capacity, the macro and meso atmospheric environmental carrying capacity in planned year, and the solutions of those mathmatical models are validated.