Cycle-by-Cycle Queue Length Estimation for Signalized Intersections Using Multi-Source Data

In order to estimate vehicular queue length at signalized intersections accurately and overcome the shortcomings and restrictions of existing studies especially those based on shockwave theory,a new methodology is presented for estimating vehicular queue length using data from both point detectors and probe vehicles. The methodology applies the shockwave theory to model queue evolution over time and space. Using probe vehicle locations and times as well as point detector measured traffic states,analytical formulations for calculating the maximum and minimum( residual) queue length are developed. The proposed methodology is verified using ground truth data collected from numerical experiments conducted in Shanghai,China. It is found that the methodology has a mean absolute percentage error of 17. 09%,which is reasonably effective in estimating the queue length at traffic signalized intersections. Limitations of the proposed models and algorithms are also discussed in the paper.

Steady-State Queue Length Analysis of a Batch Arrival Queue under N-Policy with Single Vacation and Setup Times

This paper investigates the steady state property of queue length for a batch arrival queue under N-policy with single vacation and setup times. When the system becomes empty, the server is turned off at once and takes a single vacation of random length . When he returns, if the queue length reaches or exceeds threshold , the server is immediately turned on but is temporarily unavailable due to a random setup time before offering service. If not, the server stays in the system until the queue length at least being . We derive the system size distribution and confirm the stochastic decomposition property. We also derive the recursion expressions of queue length distribution and other performance measures. Finally, we present some numerical examples to show the analytical results obtained. Sensitivity analysis is also performed.

Effects of pooling,specialization,and discretionary task completion on queueing performance

Pooling,unpooling/specialization,and discretionary task completion are typical operational strategies in queueing systems that arise in healthcare,call centers,and online sales.These strategies may have advantages and disadvantages in different operational environments.This paper uses the M/M/1 and M/M/2 queues to study the impact of pooling,specialization,and discretionary task completion on the average queue length.Closed-form solutions for the average M/M/2 queue length are derived.Computational examples illustrate how the average queue length changes with the strength of pooling,specialization,and discretionary task completion.Finally,several conjectures are made in the paper.

The Queue Length Distribution for M/G/1 Queue with Delay Single Server Vacation

In this paper we study the transient and equilibrium distributions of the queue length for the M/G/1 queueing system with delay single server vacation.By the server busy period and the Laplace transformation we directly obtain the recursion formula of the L transformation of the transient queue length distribution at any time t , as well as the recursion formula of the equilibrium distribution for calculating conveniently.Furthermore we obtain the stochastic decompositions of the queue length and waiting time in equilibrium.

THE QUEUE-LENGTH DISTRIBUTION FOR M^x/G/1 QUEUE WITH SINGLE SERVER VACATION

This paper studies the bulk-arrival M-x/G/1 queue with single server vacation. By introducing the server busy period and using the Laplace transform, the recursion expression of the Laplace transform of the transient queue-length distribution is derived. Furthermore, the distribution and stochastic decomposition result of the queue length at a random point in equilibrium are obtained. Especially some results for the single-arrival M/G/1 queue with single server vacation and bulk-arrival M-x/G/1 queue but with no server vacation can be derived directly by the results obtained in this paper.

Analysis of Stationary Queue Length Distribution for Geo/T-IPH/1 Queue

In this paper we study a Geo/T-IPH/1 queue model,where T-IPH denotes the discrete time phase type distribution defined on a birth-and-death process with countably many states.The queue model can be described by a quasi-birth-anddeath(QBD)process with countably phases.Using the operator-geometric solution method,we first give the expression of the operator and the joint stationary distribution.Then we obtain the probability generating function(PGF)for stationary queue length distribution and sojourn time distribution,respectively.

ANALYSIS OF A CONTINUOUS TIME SM[K]/PH[K]/1/FCFS QUEUE:AGE PROCESS,SOJOURN TIMES,AND QUEUE LENGTHS

This paper studies a continuous time queueing system with multiple types of customers and a first-come-first-served service discipline. Customers arrive according to a semi-Markov arrival process and the service times of individual types of customers have PH-distributios. A GI/M/1 type Markov process for a generalized age process of batches of customers is constructed. The stationary distribution of the GI/M/1 type Markov process is found explicitly and, consequently, the distributions of the age of the batch in service, the total workload in the system, waiting times, and sojourn times of different batches and different types of customers are obtained. The paper gives the matrix representations of the PH-distributions of waiting times and sojourn times. Some results are obtained for the distributions of queue lengths at departure epochs and at an arbitrary time. These results can be used to analyze not only the queue length, but also the composition of the queue. Computational methods are developed for calculating steady state distributions related to the queue lengths, sojourn times, and waiting times.

离散时间的完全服务并行优化轮询排队系统特性分析

轮询是一种依次有序服务的系统资源动态调度机制.针对服务器在站点间查询、服务和转移过程中的流水线作业方式导致了系统整体服务效率较低的问题,本文提出了完全服务的并行优化轮询系统.首先,构建了系统的单服务器多队列排队模型和相应的系统状态方程,并精确解析出系统特性参数的完整数学解析表达式.此外,还提出了一种系统状态稳定性的判定方法,对不同负载状态下的系统稳定性进行了定量分析.计算机仿真的统计分析结果与理论计算值相一致.最后,系统性能分析表明,在保持周期性、无冲突服务的基础上,系统的队长、时延特性和稳定状态下负载能力均得到了较大的提高.

连续时间完全-限定(K=2)两级轮询系统性能分析

为了实现区分网络优先级、保证公平性、提高普通站点的性能和效率,在完全-限定(K=1)两级轮询控制系统模型的基础上,提出连续时间完全-限定(K=2)两级轮询控制系统模型。在该模型中,使用限定(K=2)服务和完全服务分别对普通站点和中心站点进行服务。中心站点转换到普通站点进行服务时,使用捎带查询方式。在此基础上,采用马尔可夫链和概率母函数的数学方法建立该轮询系统模型,并推导平均排队队长和时延。利用MATLAB进行仿真实验,结果表明:理论值与仿真值误差较小,验证了理论分析的正确性;与门限-完全服务模型相比,该模型中心站点的队长和时延均小于门限-完全服务中心站点的队长和时延,具有更高的优先级;与一级完全服务和一级限定(K=2)服务模型相比,区分了优先级,性能分别提升11.7%和14.5%,说明两级服务远好于一级服务;与完全-限定(K=1)两级服务模型相比,增加了发送的数据,减少了等待时间,性能提升13.04%左右,进一步优化了普通站点的性能。

基于MEC服务器优先服务的路侧单元MAC层调度策略

针对多接入边缘计算(MEC)服务器高可靠、低时延和大数据量的数据传输要求,基于无冲突接入、优先级架构和弹性服务技术,提出一种适用于车辆边缘计算场景下的媒体访问控制(MAC)调度策略。所提策略由车联网(IoV)路侧单元(RSU)集中协调信道接入权,优先确保车载网络中车载通信单元(OBU)与MEC服务器之间的链路传输质量,以及时传输车辆到网络(V2N)业务数据;同时,对本地OBU之间的业务采取弹性服务方式,增强密集车辆接入时应急消息传输的可靠性。首先,构建调度策略的排队分析模型;其次,根据各时刻系统状态变量的无后效性特点建立嵌入式马尔可夫链,并通过概率母函数的分析方法对系统进行理论分析,得到MEC服务器通信单元和OBU的平均排队队长、平均等待时延和RSU查询周期等关键指标的精确解析表达式。计算机仿真实验结果表明,统计分析结果与理论计算结果一致,所提调度策略在高负载情况下能够提高IoV的稳定性和灵活性。

连续时间门限完全服务两级轮询系统性能分析

为区分业务优先级以及提高系统公平性与稳定性,在简化求解过程的基础上,提出一种连续时间门限完全服务两级轮询系统。系统状态由马尔科夫链得出并根据其建立数学模型,系统的平均循环周期、平均排队队长等性能参数由对数学模型的概率母函数进行求导所得,将求导结果与仿真实验进行对比,验证理论分析的准确性。将该系统与单级系统、其它两级系统进行对比,验证了该系统在保证业务优先级的同时更具公平性与稳定性。

THE TRANSIENT SOLUTION FOR M/G/1 QUEUEWITH SERVER VACATIONS

In this paper, the transient solutions for M/G/1 queues with single server vacation and multiple server vacations are firstly studied, and the recursion expressions of their Laplace transform are given. Further the distribution and stochastic decomposition result of the queue length at a random point in equilibrium are directly obtained from the transient solution. As will be seen this paper provides a intuitive and elegant method for studying transient solutions for M/G/1 queues with single server.

基于冲击波模型与YOLOv5-DeepSORT单向耦合的排队长度感知方法

针对交叉口排队长度实时感知的问题,提出一种结合交通数学模型与智能感知设备检测的排队长度感知方法。通过冲击波模型确定道路最大排队长度,将其作为以YOLOv5-DeepSORT为基础的视频感知模型的输入,实现交通数学模型与智能感知模型的单向耦合。为验证该方法的有效性和优越性,以兰州市某交叉口为例进行排队长度的实时感知,并在选定交叉口调查不同时间段的感知数据,模拟不同交叉口交通流量的差异对本研究方法感知精度的影响进行探究。研究结果表明,基于冲击波模型与YOLOv5-DeepSORT单向耦合的排队长度感知方法确定的排队长度检测区域在整体感知精度上优于对照组,平均绝对误差、均方根误差以及平均绝对百分比误差等均得到了有效降低,部分工况下精度提高40%以上。

时间敏感网络中的可变长整形队列调整算法

针对异步整形器(ATS)采用固定长度整形队列实现流量整形存在缓存资源利用率低、可调度流平均时延高等问题,提出了一种基于改进磷虾群算法与流量预测的可变长整形队列调整算法。综合考虑流的队列分配规则、有界时延需求及有限缓存资源,定义时间敏感网络中可调度流传输约束。引入混沌映射、反向学习与精英策略并设计自适应位置更新策略以提升传统磷虾群算法的求解能力,利用改进磷虾群算法寻找整形队列可调整上限。基于卷积神经网络与长短期记忆模型(CNN-LSTM)预测流量,根据预测值计算队列长度调整步幅。仿真结果表明,与采用固定长度整形队列的方法相比,所提算法能有效提高可调度流数量,降低调度流(ST)平均时延,并提升网络缓存资源利用率。

智能网联车和人驾车辆混合交通流排队长度估计模型

为了解决智能网联车(ICVs)和人驾车辆(HDVs)混行交叉口的排队估计问题,提出基于概率统计和贝叶斯定理的排队长度估计模型.综合考虑队列中智能网联车位置、速度和渗透率等因素,分别构建可观测队列排队长度估计模型、不可观测队列排队长度估计模型和渗透率估计模型,通过迭代实现排队长度和渗透率的实时估计.利用随机种子模拟不同渗透率条件下智能网联车在队列中的分布特征,分析不同交通条件下模型的估计精度.与已有模型的对比表明,在智能网联车低渗透率(10%)条件下,在非高峰时段,本研究模型、已有模型的平均绝对百分比误差(MAPE)分别为29.35%、59.68%;在高峰时段,本研究模型、已有模型的MAPE分别为26.50%、34.66%.在智能网联车高渗透率条件下(90%),在非高峰时段,本研究模型、已有模型的MAPE分别为6.90%、17.85%;在高峰时段,本研究模型、已有模型的MAPE分别为1.45%、1.05%,误差接近.本研究所提出的排队估计模型在低渗透率和高渗透率条件下均具有更好的估计精度.

C-V2X网联环境下应急优先的绿灯补偿模型研究

针对在路口实施应急车辆优先策略会对非优先相位交通造成影响的问题,在蜂窝车联网(C-V2X)环境下进行了均衡非优先相位通行效益的绿灯补偿模型研究。搭建了相应的算法模型,并对一辆应急车辆的场景进行了模拟。该模型在不影响应急车辆优先通行的前提下,根据非优先相位实时交通需求计算补偿绿灯时间,从而最小化应急优先对非优先相位的车辆通行影响。仿真结果证明,所提模型在不同的饱和度状态下均可有效地降低应急车辆通过后非优先相位车辆的平均延误时间和平均排队长度。所提模型对于应急车辆通过红绿灯路口的策略进行了优化,提高了通行效率。

到达环境可变的M/M/1排队系统

文章在经典的M/M/1排队系统模型下增加了一个可变环境因素,即顾客的到达环境A、B可以相互转化,到达时间参数将与环境同变化,利用拉普拉斯变换求环境A、B的瞬时概率,再利用概率母函数得出系统的队长分布、等待队长分布和平均队长.

具有耐烦服务员和N-策略的M/G/1可中断休假排队系统

考虑具有耐烦服务员和N-策略的M/G/1休假排队系统,其中服务员的假期可中断.运用全概率分解技术、更新理论和拉普拉斯变换工具,分析了系统的瞬态队长分布和稳态队长分布,获得了瞬态队长分布的拉普拉斯变换表达式和稳态队长分布的递推表达式,并进一步证明了稳态队长的随机分解性质.最后,通过建立费用结构模型,结合数值实例,讨论了使系统在长期单位时间内的期望费用最小的最优控制策略N*.

基于实时数据的信号交叉口评价指标模型优化研究——基于上海市浦东世纪公园周边区域的实证研究

基于实时采集的信号控制交叉口进口道运行数据,分析交叉口评价指标数学模型的准确性。通过对模型参数与指标误差的拟合关系来优化高饱和度下的数学模型,并使用不同路口的真实数据进行验证,旨在提高信号控制交叉口的评价模型精度,为智慧交通研判中的信号控制方案优化工作提供数据参考。

交叉口车流量多时段控制信息的传感融合技术

交叉口车流量随机性与不确定性导致车辆信息采集结果的差异化明显。以传感器信息融合为技术支撑,提出交叉口车流量多时段控制方法。利用多传感器采集交叉口交通信息,预处理采集到的数据。采用由指标层与目标层构成的信息融合模型,完成交通信息融合。根据信息之间的关联性聚类所有交通信息,明确分类数并划分控制时段。综合考量交叉口通行效率与环境等因素,结合排队长度、平均延误及尾气排放量建立多目标多时段控制模型,由层次分析法明确各目标权值后,采用改进萤火虫算法进行求解,实现交叉口车流量多时段控制。实验结果表明,该方法能有效改善交叉口的拥堵情况,提升通行效率,降低车流饱和度与延误时间,应用优势显著。