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741.
The limited understanding of public–private partnerships (P3s) for transportation infrastructure finance has been generally attributed to a lack of data. The more fundamental question of how P3 data are utilized in the literature is more relevant and critical, but remains unclear. This study investigates this question by examining the linkages between research objectives and data characteristics through a meta-analysis of infrastructure P3 studies using multinomial regressions. It analyzes 95 empirical studies that adopt actual data, selected from a P3 research database that includes over 345 studies and are classified into five categories including performance, contract, risk, value for money, and institutional factors. Results show that the case studies are less frequently utilized to understand P3s' institutional issues compared to those that focus on P3s' performance or VFM. Survey data are more frequently used to study P3 contracts rather than issues related to P3 project risk. We highlight the need for policy-makers to require continuing disclosure of P3 performance for validating the effectiveness of the procurement model and to improve the practice. 相似文献
742.
Turning vehicle volumes at signalized intersections are critical inputs for various transportation studies such as level of service, signal timing, and traffic safety analysis. There are various types of detectors installed at signalized intersections for control and operation. These detectors have the potential of producing volume estimates. However, it is quite a challenge to use such detectors for conducting turning movement counts in shared lanes. The purpose of this paper was to provide three methods to estimate turning movement proportions in shared lanes. These methods are characterized as flow characteristics (FC), volume and queue (VQ) length, and network equilibrium (NE). FC and VQ methods are based on the geometry of an intersection and behavior of drivers. The NE method does not depend on these factors and is purely based on detector counts from the study intersection and the downstream intersection. These methods were tested using regression and genetic programming (GP). It was found that the hourly average error ranged between 4 and 27% using linear regression and 1 to 15% using GP. A general conclusion was that the proposed methods have the potential of being applied to locations where appropriate detectors are installed for obtaining the required data. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
743.
There are many studies on container port efficiency and that seek to understand what factors, such as technical and scale efficiency, private versus public terminal management or macro-economic factors, play on the efficiency score of a given port. There are fewer studies that focus on the role played by the inter-port competitive environment. This role remains difficult to assess. In fact, on the one hand, a port subject to high inter-port competition may record higher efficiency scores due to the pressure from the competitive environment. On the other hand, a port subject to high competition may be forced to over-invest and could therefore records a lower efficiency score. This article investigates this issue and examines how the degree of competition measured at different levels (local, regional and global level) impacts the efficiency score of a given container port. To do so, we implement a truncated regression with a parametric bootstrapping model. The model applied to information gathered for 200 container ports in 2007 and 2010 leads to the following conclusions: port efficiency decreases with competition intensity when measured in a range of 400–800 km (regional level); and the effect from competition is not significant when competition is measured at a local (less than 300 km) or at a global (more than 800 km) level. Estimates also show a tendency for ports who invested from 2007 to 2010 to experience a general decrease in efficiency scores, an element which could be explained by the time lag between the investment and the subsequent potential increase in container throughput. 相似文献
744.
The focus of the current research was to evaluate how the individual’s social characteristics and urban infrastructure impacts the usage of Private Motorized Modes (PMM). Based on individual and urban characteristics a multilevel analysis was conducted on the possibility of commuting trip by private motorized modes on the rush time of 78 cities around the world. Also the selected cities were classified through a principal component analysis, and based on the classification the impact of and urban variables on the possibility of commuting trips made by private motorized modes (PCTP) was verified. Results showed a diverse range of variables related to the usage of PMM, as well as the urban structure and railway lengths being an important variable in travel behavior. 相似文献
745.
Characterizing the relationship between environmental factors and mobility is critical for developing a sustainable traffic signal control system. In this study, the authors investigate the correlation of the environmental impacts of transport and mobility measurements at signalized intersections. A metamodeling-based method involving experimental design, simulations, and regression analysis was developed. The simulations, involving microscopic traffic modeling and emission estimation with an emerging emission estimator, provide the flexibility of generating cases with various intersection types, vehicle types, and other parameters such as driver behavior, fuel types, and meteorological factors. A multivariate multiple linear regression (MMLR) analysis was applied to determine the relationship between environmental and mobility measurements. Given the limitations of using the built-in emissions modules within current traffic simulation and signal optimization tools, the metamodeling-based approach presented in this paper makes a methodological contribution. The findings of this study set up the base for extensive application of simulation optimization to sustainable traffic operations and management. Moreover, the comparison of outputs from an advanced estimator with those from the current tool recommend improving the emissions module for more accurate analysis (e.g., benefit-cost analysis) in practical signal retiming projects. 相似文献
746.
Andy H.F. Chow Alex Santacreu Ioannis Tsapakis Garavig Tanasaranond Tao Cheng 《先进运输杂志》2014,48(8):1000-1016
This paper presents an empirical assessment of urban traffic congestion in Central London, UK. Compared with freeways or motorways, urban networks are relatively less studied because of its complexity and availability of required traffic data. This paper introduces the use of automatic number plate recognition technology to analyze the characteristic of urban traffic congestion in Central London. We also present the use of linear regression to diagnose the observed congestion and attribute them to different causes. In particular, we distinguish the observed congestion into two main components: one due to recurrent factors and the other due to nonrecurrent factors. The methodologies are illustrated through a case study of Central London Area. It is found that about 15% of the observed congestion in the region is due to nonrecurrent factors such as accidents, roadwork, special events, and strikes. Given the significance of London, the study will be valuable for transport policy evaluation and appraisal in other global cities. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
747.
环境绿化目前在公路建设中越来越受到重视,它不仅能够美化环境,而且具有防护、生态保护的能力。为了充分分析、评价已建公路的工程绿化状况,对公路绿化工程进行分析评价,是非常必要和紧迫的。目前,高速、一级公路的绿化已得到普遍重视,而作为二级公路的绿化却研究得甚少。为此,本文通过对绿化功能分析,提出了二级公路绿化评价指标体系框架,该体系评价指标包括：边坡防护能力、路侧生态防护性以及景观效果;并结合我国江苏公路绿化的具体情况,提出了基于回归分析和层次分析法的二级公路绿化的评价方法,该方法运用在实践中能够客观地评价二级公... 相似文献
748.
交通分布数据获取难度大、成本高,是制约交通工程师开展交通预测的主要因素.为提高效率、降低工程实践中的预测成本,对城市路网OD矩阵可预测性展开研究.描述3种交通分布推算模型并以广州为例,给出交通流概率分布及发生量概率分布.通过回归分析及残差分析探究发生量与人口、经济的关系,提出考虑人口效益的靶向双联模型(称为TDM模型)... 相似文献
749.
为揭示交通暴露和土地利用层面各因素对新型冠状病毒肺炎(COVID-19)疫情在社区尺度传播风险的影响,以A市315个小区的1 947例COVID-19确诊数据为研究样本,利用ArcGIS平台的地理编码、核密度分析、空间统计和网络分析等方法,基于道路网络、公交网络、城市POI和中国GDP/人口空间分布的公里网格数据,获取有病例小区500m缓冲区范围内表征交通暴露和土地利用的14项具体指标。在此基础上,采用小区的COVID-19确诊人数作为解释变量,同时考虑交通暴露层面变量(路网密度、设施邻近度)和土地利用层面变量(混合度、使用强度),运用经典全局泊松回归和变系数地理加权泊松回归(GWPR)2种方法建立模型并进行实证对比分析。研究结果表明:考虑空间异质性的GWPR模型具有更高拟合优度和解释度;道路密度、公交线网密度、CBD邻近度、建筑密度、人口密度和土地价值与小区COVID-19传播风险呈显著正相关;出入口邻近度、绿地公园邻近度和土地利用混合度变量则在GWR模型中表现出随空间位置的改变呈现显著正负2种影响效果;人口密度、土地价值、绿地公园邻近度和土地利用混合度对小区COVID-19传播风险... 相似文献
750.
为指导社区生活圈打造绿色出行环境,定量解析社区建成环境对居民小汽车行驶里程(VMT)影响的空间异质性。基于建成环境的5D维度选取人口密度、土地利用多样性及公交站点密度等6个指标刻画建成环境,在《社区生活圈规划技术指南》的基础上,结合步行速度和非直线系数等指标差异化界定社区生活圈尺度,利用POI数据和道路网络等地理空间数据测度建成环境。以保定市居民出行行为调查数据作为实证研究数据来源,构建考虑自变量尺度变异的多尺度地理加权回归模型(MGWR)。研究结果表明：对比最小二乘回归(OLS)模型与传统的地理加权回归(GWR)模型,纳入变量尺度异质性的MGWR模型降低了残差的自相关性,且调整后R2相比于GWR模型与OLS模型分别提高了1.8倍与6.0倍;从标准化系数来看,社区建成环境指标中,土地利用混合度和公交服务水平对VMT影响最大;社区建成环境指标中,路网密度与交叉口密度接近全局尺度,空间异质性较弱,其余建成环境变量均具有较强的空间异质性,需要进行差异化的空间设计;社区建成环境指标局部回归系数的空间分布模式呈现“中心-外围”变化趋势,与城市形态有较强的耦合。 相似文献