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.     

An algorithm for the recognition of levels of congestion in road traffic problems

Detection and recognition of the level of congestion at an intersection is a very important problem and a valuable source of information in traffic management. Although it is just one of all the aspects that make up a traffic management system, it seems to be a crucial point for gathering information. In this paper, we present a technique based on a k-means clustering algorithm for classification, which has been already successfully used in a number of pattern recognition problems, namely: as an algorithm for face recognition problems and in a number of medical diagnosis problems and it compares very well with the state of the art techniques.     

Assessment of traffic noise and its impact on the community

Road transportation plays a major role in the economic and social development of a country. With the increase in vehicle population, noise levels will increase. This paper discusses the results of a study undertaken to assess the noise levels at the major traffic junctions of an urban city. The noise equivalent level L _eq was measured in the community areas as well as at the traffic junctions. The statistical levels L₁₀, L₅₀, L₉₀ were also measured to determine the Traffic Noise Index at the junctions. A holistic approach was adopted to study the impact of noise on the community and at the work place of an industry.     

交通系统仿真在城市规划交通影响评价中的应用前瞻

基于交通影响评价，对目前国内城市规划中存在的道路交通系统问题进行分析，剖析了目前城市规划中实施交通影响评价的意义。对交通系统仿真技术的概念和发展现状作了简单介绍，并就交通系统仿真技术在交通影响评价中的实际应用，以及交通影响评价和交通系统仿真的发展前景进行了预测。     

Role of drivers' personal characteristics in understanding traffic sign symbols

This study investigated the role of age, marital status, gender, nationality, educational background and monthly income in drivers' comprehension of traffic signs. The populations sampled here were from five Arabian Gulf Countries. A total of 28 symbolic warning and regulatory signs were investigated. A questionnaire specially prepared to collect the necessary data was distributed to over 9000 drivers in the five countries; 4774 responded (53%). The results indicated substantial problems with the level of comprehension among the drivers about the traffic signs. The percentages of drivers who correctly identified the regulatory signs and warning signs were around 55 and 56%, respectively. Age, gender, education and income played major roles in determining drivers' comprehension of signs, whereas marital status showed no significant effect. Drivers who are young, female, those with lower levels of education or lower incomes understand the signs significantly worse than drivers who are older, male, with higher levels of education or higher incomes. Drivers from Europe and USA are significantly better than Asian and Arab drivers. These findings are believed to be important for the designers of road signs for international applications.     

Derivation of a clinical decision rule for whiplash associated disorders among individuals involved in rear-end collisions

A prospective study was used to: (1) quantify potential risk factors for whiplash associated disorder following a rear-end motor vehicle collision; and (2) develop a simple clinical decision rule for the early identification of patients at risk for long-term whiplash associated disorder. Between 1 October 1995 and 31 March 1998, 446 adults involved in rear-end collisions presented to the only two emergency departments serving Kingston, Ontario. Eligible and consenting subjects (n = 353) were contacted by telephone soon after the collisions then at multiple occasions up to 2 years post-collision. Bivariate and multiple logistic regression analyses were used to identify potential risk factors for persistent symptoms. A software package that uses Chi-squared automatic interaction detection and classification and regression trees was used to develop a simple clinical decision rule for the identification of patients at high and low risk for persistent whiplash associated disorder. Risk factors identified by regression analyses included: increased age, number of initial physical symptoms, and early development of the following symptoms: upper back pain, upper extremity numbness or weakness, or disturbances in vision. A simple clinical decision rule that requires asking up to three basic questions of each patient was derived and would have identified the 118 cases of persistent whiplash associated disorder with a sensitivity of 91.5% (95% confidence interval: 86.5, 96.6) and a specificity of 51.4% (44.7, 58.1). This study confirmed the importance of several risk factors for whiplash associated disorder following rear-end motor vehicle collisions.     

Differences in cause-specific patterns of unintentional injury mortality among 15-44-year-olds in income-based country groups

OBJECTIVES: The aim of the present study was to investigate the cause-specific patterns of unintentional injury mortality among 15-44-year-olds in various income-based country groups, and to analyze which specific causes contribute the most to the unintentional injury mortality in each country group. MATERIALS AND METHODS: Cross-sectional data on the five most common causes of unintentional injury mortality by age-sex specific subgroups were compiled for 57 countries from the World Health Statistics Annuals for the year 1993 (1991-1994 if information for 1993 was unavailable). Data were categorized into four income-based country groups according to their gross national product (GNP) per capita for the year 1993. The differences between means and rate ratios of low, lower-middle, and upper-middle income countries were calculated by comparing them with those of the high-income countries. Regression analysis was performed to determine the trends in the direction of income for each specific cause of unintentional injury mortality by age-sex. RESULTS: For any of the specific causes of unintentional injury mortality there was an inverse relationship between mortality rates and GNP per capita except for motor vehicle traffic (MVT) among the 15-24-year-old age group. MVT accidents were the most common cause and contributed 26-77% of all unintentional injury mortality. The second most common cause was poisoning in all country groups except low-income countries where drowning dominated for males and mixed causes for females. Upper-middle income countries represented the highest MVT mortality in all age-sex subgroups except among 15-24-year-old females for which high-income countries displayed the highest rate. For other causes, lower-middle income represented the highest rates with a few exceptions. In the 15-24-year age group, the rate ratio of motor vehicle traffic mortality was higher in high-income countries compared to low-income countries, while in the 35-44-year age group, all other country groups showed a higher rate ratio than high-income countries. Drowning for males and burns for females in the low and middle-income countries were significantly higher than in high-income countries.     

Characteristics of low speed accidents with buses in public transport

Low-speed accidents with buses in public transport in the city of Uppsala during the years 1986-2000 are coded in 17 variables concerning mainly physical properties of the accident. The taxonomy uses classifications from existing schemes, but some are altered and some new are added to capture common features of reports of bus accidents in this population. It is found that side contacts and singles are the most common accidents, and that more than a quarter of all accident involvements occurs at bus stops. Inter-rater reliability calculations for the categories show that all except one have reliabilities above 80%. The level of internal validity, calculated as agreement of frequencies between time periods, is acceptable, despite many possible sources of change and bias. It is argued that the validity of this database far exceeds that of the, for research purposes normally used, non-company self-reports, state- and police-archives, due to more extensive reporting and corroborating evidence. The practical usefulness of these results and accident taxonomies in general is discussed.     

多业务网络流量工程模型研究

文章详细分析了多业务网络流量工程的一个通用模型和它的基本功能,系统分析了网络实际存在的流量波动问题及其对网络规划的影响。     

对网络QoS中拥塞控制的研究

拥塞控制是解决网络拥塞问题的重要策略。本文主要从流量预测和流量整形两个方面提出了降低拥塞率的通用方法,对传统的漏桶算法和RED算法做了改进,使得它们在降低拥塞率的同时又照顾到了公平性和效率。