Parallel solution of a traffic flow simulation problem

Computational Fluid Dynamics (CFD) methods for solving traffic flow continuum models have been studied and efficiently implemented in traffic simulation codes in the past. This is the first time that such methods are studied from the point of view of parallel computing. We studied and implemented an implicit numerical method for solving the high-order flow conservation traffic model on parallel computers. Implicit methods allow much larger time-step than explicit methods, for the same accuracy. However, at each time-step a nonlinear system must be solved. We used the Newton method coupled with a linear iterative method (Orthomin). We accelerated the convergence of Orthomin with parallel incomplete LU factorization preconditionings. We ran simulation tests with real traffic data from an 12-mile freeway section (in Minnesota) on the nCUBE2 parallel computer. These tests gave the same accuracy as past tests, which were performed on one-processor computers, and the overall execution time was significantly reduced.     

Modelling the Spatio-Temporal Distribution of Ambient Nitrogen Dioxide and Investigating the Effects of Public Transit Policies on Population Exposure

Estimating the future state of air quality associated with transport policies and infrastructure investments is key to the development of meaningful transportation and planning decisions. This paper describes the design of an integrated transportation and air quality modelling framework capable of simulating traffic emissions and air pollution at a refined spatio-temporal scale. For this purpose, emissions of Nitrogen Oxides (NO_x) were estimated in the Greater Montreal Region at the level of individual trips and vehicles. In turn, hourly Nitrogen Dioxide (NO₂) concentrations were simulated across different seasons and validated against observations. Our validation results reveal a reasonable performance of the modelling chain. The modelling system was used to evaluate the impact of an extensive regional transit improvement strategy revealing reductions in NO₂ concentrations across the territory by about 3.6% compared to the base case in addition to a decrease in the frequency and severity of NO₂ hot spots. This is associated with a reduction in total NO_x emissions of 1.9% compared to the base case; some roads experienced reductions by more than half. Finally, a methodology for assessing individuals’ daily exposure is developed (by tracking activity locations and trajectories) and we observed a reduction of 20.8% in daily exposures compared to the base case. The large difference between reductions in the mean NO₂ concentration across the study domain and the mean NO₂ exposure across the sample population results from the fact that NO₂ concentrations dropped largely in the areas which attract the most individuals. This exercise illustrates that evaluating the air quality impacts of transportation scenarios by solely quantifying reductions in air pollution concentrations across the study domain would lead to an underestimation of the potential health gains.     

驾驶员与儿童事故倾性研究

文章通过对全国部分城市驾驶员交通事故和儿童意外伤害事故的流行病学研究结果发现：（１）驾驶员交通事故和儿童意外伤害事故检出率不存在地区性差异；（２）驾驶员交通事故和儿童意外伤害事故的检出率无显著性的年龄差异；（３）不同年龄段驾驶员和儿童，男性事故检出率均高于女性事故检出率；（４）极少数的事故人群具有事故倾向性：在驾驶人群中有６％～８％的事故倾性驾驶员，其引起的交通事故数占总事故数的３０％～４０％，在１～１４岁儿童中有１％～２％的事故倾性儿童，其发生的意外伤害数占意外伤害总数的２５％～３５％；（５）事故倾性驾驶员和事故倾性儿童再发事故的比率均比对照组高。文章从流行病学角度证实了事故倾性人群的存在，并对事故倾性的本质作了初步探讨。     

Personality and attitudes as predictors of risky driving among older drivers

Although there are several studies on the effects of personality and attitudes on risky driving among young drivers, related research in older drivers is scarce. The present study assessed a model of personality-attitudes-risky driving in a large sample of active older drivers. A cross-sectional design was used, and structured and anonymous questionnaires were completed by 485 older Italian drivers (Mean age = 68.1, SD = 6.2, 61.2% males). The measures included personality traits, attitudes toward traffic safety, risky driving (errors, lapses, and traffic violations), and self-reported crash involvement and number of issued traffic tickets in the last 12 months. Structural equation modeling showed that personality traits predicted both directly and indirectly traffic violations, errors, and lapses. More positive attitudes toward traffic safety negatively predicted risky driving. In turn, risky driving was positively related to self-reported crash involvement and higher number of issued traffic tickets. Our findings suggest that theoretical models developed to account for risky driving of younger drivers may also apply in the older drivers, and accordingly be used to inform safe driving interventions for this age group.     

Effective edge node configuration for video transport over Optical Burst Switched networks

This paper considers digital video transport over Optical Burst Switched networks where burst losses cause data loss from one or more adjacent video frames. Analytical approximations for the frame losses and video playback interruptions are derived and validated using simulations. Both parameters require a very limited and static amount of data about the video on the user side and some quality of service metrics about the network to quantify the quality of the received video. The results take into account the strong dependency in the video traffic structure due to the coding mechanisms. The critical effect of video coding parameters is also revealed. The paper also presents a Traffic Engineering procedure to select the best parameters for the edge node and the video codec to meet a given video quality level on the user side.     

电信建筑的有效面积利用率和交通组织

通过工程实例阐明提高电信建筑的有效面积利用率和合理规划交通组织是提高投资效益的重要途径。     

Impact of Annual Average Daily Traffic on Highway Runoff Pollutant Concentrations

The objective of this study was to evaluate correlations between annual average daily traffic (AADT) and storm water runoff pollutant concentrations generated from California Department of Transportation (Caltrans) highway sites. Analyses of data collected from the Caltrans four-year (1997–2001) highway runoff characterization program revealed that, in general, pollutant concentrations from urban highways were higher than those found from nonurban highways. For a limited number of pollutants, however, the concentrations from nonurban highways were found to be higher than the concentrations from urban highways. No direct linear correlation was found between highway runoff pollutant event mean concentrations and AADT. However, through multiple regression analyses, it was shown that AADT has an influence on most highway runoff constituent concentrations, in conjunction with factors associated with watershed characteristics and pollutant build-up and wash off. The other noticeable factors shown to influence the accumulation of pollutants on highways were antecedent dry period, drainage area, maximum rain intensity, and land use.     

EWSD(V9)中文话务统计管理软件

ＥＷＳＤ交换机已从Ｖ６．２版本升级为Ｖ９版本，两版本在话务数据和功能方面有很大改进与不同。文章介绍了Ｖ９版本在输出话务数据方面增加的新内容。     

探讨城市综合体的设计模式——以“江西上饶星河国际电影城”为例

近年来,虽然国家调控房地产,但是城市综合体仍然迅速地发展。本文在概述城市综合体的概念和构成特点后,以江西上饶星河国际电影城为例,对其功能的整合、交通的组织、空间的营造等方面进行分析研究,粗浅地探讨城市综合体的设计方法,以期完善城市综合体的理论构成。