交通发生吸引源集聚影响下路网宏观基本特性

Macroscopic basic characteristics of a road network under the influence of traffic generation and attraction source agglomeration

宏观基本图不受路网外部交通发生吸引源的影响,描述了匀质性路网内累积车辆数与路网旅行完成率之间的关系,可直观表达路网宏观基本特性.然而,当路网内交通发生吸引源发生变化时,会影响路网交通密度,从而对宏观基本特性产生影响.为了分析交通发生吸引源不同集聚状态对宏观基本图的影响规律,以交通发生吸引源发生吸引量和路段阻抗为参数,建立交通发生吸引源聚集度模型.以方格式路网为分析对象,设计9组不同交通发生吸引源方案,通过对比交通发生吸引源聚集度与路网宏观基本图曲线,发现只有当路网处于拥挤流状态时,交通发生吸引源聚集现象才会对宏观基本图产生影响,并且路网中交通发生吸引源聚集度越低(交通发生吸引量分布越均衡),路网旅行完成率就会越高.

The macroscopic fundamental diagram(MFD),which can describe the macroscopic state of a regional network intuitively,describes a unimodal,statistical and reproducible relationship between accumulation and the trip completion flow of a region.Existing researches have proved that using MFD characteristics can’metering’the boundary flow and relieve the traffic congestion problem effectively.As the foundation of traffic control,existing studies on the characteristic of MFD have proved that external origin to destination demand does not influence the MFD distribution.However,the traffic generation and attraction sources in the regional road networkwill changes the distribution of traffic density of the road network,thus affecting the characteristic of MFD.However,to date,no related analysis explored the influence of the traffic generation and attraction sourcesin the regional road network.To solve this problem,according to the spatial and temporal distribution of traffic generation and attraction sources in the regional road network,this paper puts forward an aggregation degree index analysis model of traffic generation and attraction sources,based on the dynamic parameters of traffic generation and attraction sources,and section traffic impedance.Taking a square-format road network as the target,nine groups of schemes for different traffic generation and attraction sources are designed.Two conclusions can be drawn after comparing the MFD curve of the road network under different aggregation degree index of traffic generation and attraction sources:(1)when the traffic flow of the road network is in the state of free flow or critical flow,the aggregation effect of traffic generation and attraction sources has no effect on MFD distribution;(2)when the traffic flow of the road network is in the congestion flow state,the aggregation effect of traffic generation and attraction sources influences MFD distribution.Moreover,under the same road network flow conditions,the aggregation degree of traffic generation and attraction sources is lower in the road network(the distribution of traffic generation and attraction volume is more balanced),the trip completion flow of road network will be higher.Otherwise,the aggregation degree of traffic generation and attraction sources is higher in the road network(the distribution of traffic generation and attraction volume is more unbalanced),the trip completion flow of road network will be lower.