Large-scale application of MILATRAS: case study of the Toronto transit network

This paper documents the efforts to operationalize the conceptual framework of MIcrosimulation Learning-based Approach to TRansit Assignment (MILATRAS) and its component models of departure time and path choices. It presents a large-scale real-world application, namely the multi-modal transit network of Toronto which is operated by the Toronto Transit Commission (TTC). This large-scale network is represented by over 500 branches with more than 10,000 stops. About 332,000 passenger-agents are modelled to represent the demand for the TTC in the AM peak period. A learning-based departure time and path choice model was adopted using the concept of mental models for the modelling of the transit assignment problem. The choice model parameters were calibrated such that the entropy of the simulated route loads was optimized with reference to the observed route loads, and validated with individual choices. A Parallel Genetic Algorithm engine was used for the parameter calibration process. The modelled route loads, based on the calibrated parameters, greatly approximate the distribution underlying the observed loads. 75% of the exact sequence of transfer point choices were correctly predicted by the off-stop/on-stop choice mechanism. The model predictability of the exact sequence of route transfers was about 60%. In this application, transit passengers were assumed to plan their transit trip based on their experience with the transportation network; with no prior (or perfect) knowledge of service performance.     

Simulating the impacts of household travel on greenhouse gas emissions,urban air quality,and population exposure

This paper establishes a link between an activity-based model for the Greater Toronto Area (GTA), dynamic traffic assignment, emission modelling, and air quality simulation. This provides agent-based output that allows vehicle emissions to be tracked back to individuals and households who are producing them. In addition, roadway emissions are dispersed and the resulting ambient air concentrations are linked with individual time-activity patterns in order to assess population exposure to air pollution. This framework is applied to evaluate the effects of a range of policy interventions and 2031 scenarios on the generation of vehicle emissions and greenhouse gases in the GTA. Results show that the predicted increase of approximately 2.6 million people and 1.3 million jobs in the region by 2031 compared to 2001 levels poses a major challenge in achieving meaningful reductions in GHGs and air pollution.     

Analysis of the environmental benefits of a motorcycle idling stop policy at urban intersections

In an attempt to reduce CO₂ emissions from motorized transport, the Taiwanese government introduced an idling stop policy for vehicles in early 2007. This paper seeks to quantify the environmental benefits of the policy based on a stated preference analysis. Motorcyclists were surveyed at urban intersections in Taiwan, to identify the amount of time they would be willing to turn off their engines while waiting at traffic lights (the WTO). A contingent valuation framework based on stated preference questions was designed to determine the WTO. Results obtained from the Spike model showed that the average motorcyclist’s WTO is 82 s. In another analysis, in which other variables were taken into consideration, such as the possibility that the policy will be enacted as legislation, the expected WTO increased to 101 s. In both cases, an idling stop policy would have positive environmental effects, reducing gasoline usage by 1021 L per hour and reducing CO₂ emissions by 0.56 metric tons per hour at the intersection studied during peak periods.     

Discretionary activity location choice: in-home or out-of-home?

This paper examines the location choice associated with discretionary activities (in-home vs. out-of-home). These substitution patterns are important in terms of travel demand as in-home activities do not necessitate travel while out-of-home activities incur travel. Mixed logit models are estimated using an activity dataset (2003 CHASE data) to analyze the factors associated with this choice at the individual activity-level. Results suggest that the attributes of an activity significantly contribute to understanding the likelihood of engaging in out-of-home activities. Activity type interaction terms reveal the varying influence that socio-demographics, activity attributes and travel have over four different activity types modeled. The results reveal that the location choice (in-home vs. out-of-home) is sensitive to travel characteristics. As the travel time and cost increases, an individual is less likely to engage in an activity out-of-home. Compared to passive and social activities, the location of active activities is more sensitive to changes in travel attributes.     

Analysis of cost estimation disclosure in environmental impact statements for surface transportation projects

Reliability in cost estimates in publicly funded projects is more important today than ever with increased governmental funding to infrastructure projects and associated accountability requirements, but surface transportation projects, large and small, in the United States have a legacy of cost overruns. The problems with these overruns start with the cost estimation process before projects begin. Studies have shown that early cost estimations reflect best-case scenarios rather than realistic expectations, and have attributed technical, economic, psychological, and political reasons for underestimation. The primary objectives of this research were to determine how costs have been presented and updated in environmental impact statements, to identify endemic technical problems with cost estimation during the environmental review of surface transportation projects, and to develop recommendations for improving cost estimation and disclosure. Cost estimation methods were analyzed from the documents of 100 projects, including draft environmental impact statements, final environmental impact statements, and records of decision. The study concluded that the lack of guidance on how to include cost estimation in environmental review revealed itself in the level of detail and attention given to estimating costs. Agencies omitted or included various aspects of cost estimation randomly. Professional organizations should fill the gap of the need for specific guidance to cost estimation for environmental review so it can evolve as a state of the practice.     

Managing passenger behavioral intention: an integrated framework for service quality,satisfaction, perceived value,and switching barriers

This paper seeks to improve our understanding of passengers’ behavioral intention by proposing an integrated framework from the attitudinal perspective. According to the literature in marketing research, we establish a causal relationship model that considers “service quality-satisfaction-behavioral intentions” paradigm, perceived value theory, and switching barrier theory. Exploring passengers’ behavioral intention from satisfaction and perceived value help to understand how passengers are attracted by the company, while switching barriers assist in realizing how passengers are “locked” into a relationship with the current company. Furthermore, in order to capture the nature of service quality, we adopt a hierarchical factor structure which serves service quality as the higher-order factor. In this study, coach industry is selected as our research subject. The empirical results, as hypothesized, show that all causal relationships are statistically significant, and perceived value us the most important predictor of satisfaction and passengers’ behavioral intention. In conclusion, the managerial implications and suggestions for future research are discussed.     

输水盾构隧洞复合衬砌结构设计计算研究

软土有压输水盾构隧洞采用管片外衬和整筑预应力内衬作复合式衬砌的设计计算中,为能较好考虑内衬与外衬管片的相互作用,以及内衬预应力荷载在隧洞施工和运营各阶段对复合衬砌结构受力的影响,本文提出了一种新的实体叠合计算模型。由于确定管片纵缝接头抗弯刚度的复杂性,文中建议对用数值模拟管片纵缝接头刚度采用了一种非线性耦合弹簧＂接触对＂的模拟系统。在采用实体单元建模的条件下,由于计入管片接头刚度的力学处理困难,文中研究了一种能以模拟管片接头刚度的简化计算方法。根据内、外衬砌接触界面处理方式的不同,文中提出了5种适合不同界面条件内、外层衬砌的相互作用模型。此外,本文还研制了内衬预应力荷载的一种转化程序,以解决采用等效荷载法施加预应力时的前处理问题。上述各点创意构思已在南水北调中线一期穿黄隧洞的结构设计研究中得到了具体反映和成功应用。     

陡坡富水斜井仰拱施工技术

大相岭泥巴山隧道2#通风斜井左线全长909.38 m、倾角17°29′19″(坡度31.5%),右洞斜井912.7 m、倾角16°41′12″(坡度30%),采用有轨运输系统,地质情况复杂,日涌水量达27 000 m3/d。文章介绍了长大陡坡富水斜井仰拱施工技术,采用先浇筑仰拱两侧墙角处边墙混凝土,完善了排水系统,保护了拱脚,使得仰拱能够全幅一次浇筑,确保了混凝土质量,并使结构安全稳定及工程稳步推进,加快了施工进度,颇值类似工程借鉴。     

运用灰色理论预测隧道变形的探讨

隧道变形监测对于隧道的安全有着重要的作用.运用灰色理论GM模型对其变形数据进行预测分析,发现灰色理论对隧道的变形有一定的预测效果,同时了解到不同样本数据其预测精度存在差异.为此,提出使用二次拟合参数法对其进行改进,得出二次拟合参数法对低精度的预测模型有一定的改进效果,而对于较高精度的预测模型效果并不显著.     

电机软开关逆变控制系统的设计与实现

传统的逆变器开关管工作在硬开关状态下,存在诸多的弊端,克服这些缺点的有效方法是软开关技术.将一种新型的直流环节并联谐振软开关逆变器应用于基于CAN通信的交流电机调速系统中,组成了交流电机软开关逆变控制系统,阐述了其原理、拓扑及特点.在系统中,上位机(PC)通过CAN总线与下位机(TMS320 LF2407)实时通信,下位机通过SVPWM控制逆变器.使用LabWindows/CVI 6.0开发了控制软件,通过实验,对硬开关和软开关条件下电机的运行性能进行了对比,证明软开关技术具有明显的优势.