A macroscopic theory of two-lane rural roads

A macroscopic theory for predicting the operation on two-lane, two-way roads is proposed. In this theory, the interaction between fast and slow vehicles obeys Newell’s kinematic wave theory of moving bottlenecks. Calibration is not required as all parameters are fully observable. Closed-form expressions for the capacity, average speed, percent time spent following and overtaking rates are proposed and the biases of current practice are identified. Comparisons between the proposed theory and empirical data are also included.     

Variable speed limit control for severe non-recurrent freeway bottlenecks

Variable speed limit (VSL) schemes are developed based on the Kinematic Wave theory to increase discharge rates at severe freeway bottlenecks induced by non-recurrent road events such as incidents or work zones while smoothing speed transition. The main control principle is to restrict upstream demand (in free-flow) progressively to achieve three important objectives: (i) to provide gradual speed transition at the tail of an event-induced queue, (ii) to clear the queue around the bottleneck, and (iii) to discharge traffic at the stable maximum flow that can be sustained at the bottleneck without breakdown. These control objectives are accomplished without imposing overly restrictive speed limits. We further provide remedies for (a) underutilized bottleneck capacity due to underestimated stable maximum flow and (b) a re-emergent queue at the bottleneck due to an overestimated stable maximum flow. We analytically formulate the reductions in total delay in terms of control parameters to provide an insight into the system performance and sensitivity. The results from the parameter analysis suggest that significant delay savings can be realized with the proposed VSL control strategies.     

城市轨道交通运能瓶颈识别方法研究

城市轨道交通庞大的客流量导致了运能紧张及能力利用不合理的现象,严重影响了系统的整体运行效率。针对运能瓶颈问题进行分析,给出了车站瓶颈静态识别模型;结合能力利用公式和AnyLogic仿真软件,对车站的动态瓶颈进行了研究;对于区间线路瓶颈,提出了基于客流的识别方法;进一步分析了车站内部瓶颈以及车站、线路间瓶颈的动态传播变化规律。最后进行了实例应用,结果表明,复兴门站的车站瓶颈为站台层的换乘楼梯口处,2号线各区间的能力利用率相差不大,线路瓶颈最大值出现在建国门至朝阳门这一区间。该方法考虑了车站和线路不同位置的特性,并提出了相应的瓶颈识别思路,具有良好的实用价值。      

铁路客运站高架匝道落客区通行能力分析

铁路客运站高架匝道落客区通行能力直接影响着匝道通行能力,从而在总体上制约着高架的交通运行状况。在铁路客运站落客区及部分高架匝道交通流数据调查的基础上,分析高架匝道落客区交通流特性以及落客区通行能力的影响因素。建立铁路客运站高架匝道落客区通行能力计算模型,并标定车辆排队概率、车辆平均停靠时间、停留时间、乘客服务时间等相应参数。     

Local ramp metering with distant downstream bottlenecks: A comparative study

The well-known feedback ramp metering algorithm ALINEA can be applied for local ramp metering or included as a key component in a coordinated ramp metering system. ALINEA uses real-time occupancy measurements from the ramp flow merging area that may be at most a few hundred meters downstream of the metered on-ramp nose. In many practical cases, however, bottlenecks with smaller capacities than the merging area may exist further downstream, which suggests using measurements from those downstream bottlenecks. Recent theoretical and simulation studies indicate that ALINEA may lead to poorly damped closed-loop behavior in this case, but PI-ALINEA, a suitable Proportional-Integral (PI) extension of ALINEA, can lead to satisfactory control performance. This paper addresses the same local ramp-metering problem in the presence of far-downstream bottlenecks, with a particular focus on the employment of PI-ALINEA to tackle three distinct cases of bottleneck that may often be encountered in practice: (1) an uphill case; (2) a lane-drop case; and (3) an un-controlled downstream on-ramp case. Extensive simulation studies are conducted on the basis of a macroscopic traffic flow model to show that ALINEA is not capable of carrying out ramp metering in these bottleneck cases, while PI-ALINEA operates satisfactorily in all cases. A field application example of PI-ALINEA is also reported with regard to a real case of far downstream bottlenecks. With its control parameters appropriately tuned beforehand, PI-ALINEA is found to be universally applicable, with little fine-tuning required for field applications.     

基于Domino的OA系统调优

针对基于Domino的OA系统当前存在的性能问题进行分析,找出造成性能瓶颈的原因,并提出可行的解决方案来优化性能。     

农村农副产品流通网络构建与研究

本文通过分析我国农村基层农副产品流通网络的现状与特点,发现存在的问题与不足。并针对当前状况,提出新时期农村基层农副产品流通网络构建思路,以便更好地为我国进行“三农”建设服务。     

Platoon-based traffic flow model for estimating breakdown probability at single-lane expressway bottlenecks

This study investigates the mechanism of traffic breakdown and establishes a traffic flow model that precisely simulates the stochastic and dynamic processes of traffic flow at a bottleneck. The proposed model contains two models of stochastic processes associated with traffic flow dynamics: a model of platoon formation behind a bottleneck and a model of speed transitions within a platoon. After these proposed models are validated, they are applied to a simple one-way, one-lane expressway section containing a bottleneck, and the stochastic nature of traffic breakdown is demonstrated through theoretical exercises.     

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已有的求解股道分配问题的方法很少探讨强壮性,得到的股道分配方案中会有一些瓶颈. 要对这些瓶颈进行局部优化,就需要一定的方法来探测这些瓶颈. 本文首先利用Petri网技术将一个股道分配方案转换成可执行的动态模型,然后对每一项列车作业进行扰动分析,并利用全部列车的出发晚点时间来识别瓶颈. 最后,对一个衔接6个方向的车站平面图和一个持续时间约30分钟的股道分配方案进行分析,结果发现最小缓冲时间为21秒;方案中存在两处瓶颈,缓冲时间分别为57秒和44秒,这表明最小缓冲时间所对应的列车作业区域不一定是方案的瓶颈. 这种方法为强壮性优化以及多方案比选提供了技术支持.