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1.
A macroscopic model for dynamic traffic flow is presented. The main goal of the model is the real time simulation of large freeway networks with multiple sources and sinks. First, we introduce the model in its discrete formulation and consider some of its properties. It turns out, that our non-hydrodynamical ansatz for the flows results in a very advantageous behavior of the model. Next the fitting conditions at junctions of a traffic network are discussed. In the following sections we carry out a continuous approximation of our discrete model in order to derive stationary solutions and to consider the stability of the homogeneous one. It turns out, that for certain conditions unstable traffic flow occurs. In a subsequent section, we compare the stability of the discrete model and the corresponding continuous approximation. This confirms in retrospection the close similarities of both model versions. Finally we compare the results of our model with the results of another macroscopic model, that was recently suggested by Kerner and Konhäuser [Phys. Rev. E 48, 2335–2338 (1993)]. 相似文献
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3.
This paper assumes that activities at the home and work location are important determinants of individuals' paths through time and space. Fixed activities at these locations determine to a large extent the duration and timing of time windows – blocks of time available for participation in travel and out-of-home non-work activities. Taking the time spent at home and at the workplace as a starting point, this paper classifies activity patterns on workdays into six groups with distinct home- and work-stay patterns. For this, data are used from the 1998 Netherlands National Travel Survey. The six clusters vary in terms of the duration and timing of time windows and some of the differences can be explained by commute characteristics, types of non-work activities performed, workers' sociodemographic attributes, and their spatiotemporal environment. However, the impact of sociodemographic and spatiotemporal variables on cluster membership is shown to be weak. 相似文献
4.
In the United States, federal funding for public transit often accounts for a large proportion of a local agency's budget, especially for capital investments. For this reason, local governments can be expected to plan a portfolio of projects that maximize federal contributions. This study examines the financial effects of federal transit subsidy policy on local transit investment decisions. Data from a System Planning Study for the Geary Corridor in San Francisco are used as an illustration. It is found that federal transit subsidy policy provides financial incentives for local decision-makers to select capital-intensive investment options that may not be efficient or effective. While federal financial incentives are not the only factor influencing local investment decisions, some reform of the current subsidy policy may be necessary to reduce the incentive for ineffective use of public resources. 相似文献
5.
Luis F. Miranda-Moreno Naveen Eluru Martin Lee-Gosselin Tyler Kreider 《Transportation》2012,39(5):895-918
This paper presents an approach to investigating the impact of information and communication technologies (ICTs) on travel behaviour and its environmental effects. The paper focuses on the spatial dispersion of out-of-home activities and travel (activity space) and greenhouse gas emissions (GHGs) at the level of the individual. An original method, combining spatial analysis in a geographic information system with advanced regression techniques, is proposed to explore these potentially complex relationships in the case of access to mobile phones and the internet, while taking into account the influence of socio-economics and built environment factors. The proposed methodology is tested using a 7-day activity-based survey in Quebec City in 2003?C2004, a juncture of particular interest because these ICTs had recently crossed the threshold of 40?% (mobile phone) and 60?% (home-based internet) penetration at the time. The study period also largely pre-dates the era of mobile internet access. Among other results, socio-demographic factors were found to significantly affect both ICT access and travel out-comes. The built environment, represented by neighbourhood typologies, also played an important role. However, it was found that after controlling for the self-selection effect, built environment and socio-demographics, those who had a mobile phone available produced 30?% more GHGs during the observed week than those who did not. This higher level of GHG pro-duction was accompanied by a 12?% higher measure of activity dispersion. On the other hand, having internet access at home was associated with lower GHGs (?19?%) and lesser activity dispersion (?25?%). Possibly, mobile phones enable individuals to cover more space and produce more emissions, while the internet provides opportunities to stay at home or avoid motorized travel thus reducing emissions. The estimated effects of having a mobile phone were not only negative but also larger in magnitude from the environmental point of view than those of fixed internet access. However, the results of this study also suggest that access to mobile phones and internet may have substantial and compensatory effects at the individual level that are undetected when using model structures that do not take into account that unobserved factors may influence both ICT choices and travel outcomes. 相似文献
6.
Martin Eriksson Nikolaos P. Papanikolopoulos 《Transportation Research Part C: Emerging Technologies》2001,9(6):142
In this paper, we describe a system that locates and tracks the eyes of a driver. The purpose of such a system is to perform detection of driver fatigue. By mounting a small camera inside the car, we can monitor the face of the driver and look for eye movements which indicate that the driver is no longer in condition to drive. In such a case, a warning signal should be issued. This paper describes how to find and track the eyes. We also describe a method that can determine if the eyes are open or closed. The primary criterion for this system is that it must be highly non-intrusive. The system must also operate regardless of the texture and the color of the face. It must also be able to handle changing conditions such as changes in light, shadows, reflections, etc. Initial experimental results are very promising even when the driver moves his/her head in a way such that the camera does not have a frontal view of the driver’s face. 相似文献
7.
从穿越瑞士列奇堡隧道的挤压变形性极强的碳质页岩带的经验中,可以得出下述结论:圆形含承压单元的支护截面,其收敛变形性总趋势要比马蹄形不含承压单元的支护截面小;圆形支护截面与马蹄形支护截面的变形性没有本质的区别;由于山体构造的不均一性,导致开挖断面的不规则变形,这是使承压单元过早脱落的原因。 相似文献
8.
Sales tax measures passed at the local level and dedicated to transportation projects have become increasingly popular in
the United States. While revenues from fuel taxes stagnate, growth of local transportation sales taxes (LTSTs), most approved
in local elections, has led to a gradual shift of the financial base for transportation projects away from user fees and toward
broader-based taxes. In this study, the relationship between voter support and the social, political, and geographic characteristics
of the voters is explored. Using precinct-level voting data and census demographic data for three local transportation sales
tax elections in Sonoma County, in the San Francisco Metropolitan area of California, regression models were constructed to
analyze this relationship. In addition, the relationship between the outcomes of the three measures was explored to better
understand which transportation projects might have garnered more support for the successful measure. It was found that the
closer voters lived to the transportation projects to be funded, the greater their support. Higher incomes were also positively
related to support, controlling for other variables. Political leanings were found to affect support, with the direction of
the effect dependent upon the project list in each measure’s expenditure plan. Finally, it appears that the latest measure,
which passed successfully, benefited greatly from its multi-modal expenditure plan. 相似文献
9.
Abstract The City of Edinburgh in Scotland in the UK had advanced plans for a congestion charging scheme until 25 February 2005. However, these plans were abandoned at that time after a referendum that resulted in a ‘no vote’. This paper explains the origins of the scheme, outlines its nature, extent, charging technology and predicted effect; it also analyses the difficulties that exist when attempting to plan and implement such a scheme in a particular governance context, and when there is little unanimity of public opinion about the need for a scheme. As well as the primary documentation from the proposals (e.g. public inquiry submissions, papers to government), the paper also draws upon a series of face-to-face interviews that were undertaken with key stakeholders. It also provides an analysis of press coverage in the local (Edinburgh) and national (Scottish) newspapers in the run-up to the referendum. These sources explain both the systemic and more local barriers to the scheme's implementation. The paper draws key lessons which are important for authorities considering the implementation of a road user charging scheme, by suggesting how legislative and governance barriers to implementation can be reduced. The lessons are of relevance world wide. 相似文献
10.
Recently, there has been a surge of interest in Tradable Credits (TC) as an alternative measure to manage the growth of personal car use. This paper summarises the results and methodologies of studies that have sought to anticipate the behavioural responses to several proposed TC schemes that target personal travel. In a critical reflection on this work and in an attempt to inspire future research, we argue that future empirical studies on TC behaviours can greatly benefit from insights from the fields of behavioural economics and cognitive psychology. Therefore, in the second part of the paper, we bring together behavioural concepts from these fields that are relevant in a TC decision-making context. Based on observations from current TC studies and the behavioural mechanisms identified in the second part of the paper, we propose promising directions for future research on understanding the impact of TC on personal car travel. 相似文献