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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Studies of traffic oscillations: a behavioral perspective

Chen, Danjue 30 May 2012 (has links)
Traffic oscillations, or simply stop-and-go waves, are a common phenomenon arising in congested traffic but still not well understood. This phenomenon causes broad adverse impacts to safety risk, fuel efficiency and greenhouse emission. To eliminate or reduce those impacts, understanding the cause and propagation mechanism is essential. This dissertation studied driving behavior in traffic oscillations with the objective to uncover the formation and propagation mechanism of traffic oscillations. This study establishes a behavioral car-following model, the Asymmetric Behavioral model, based on empirical trajectory data that is able to reproduce the spontaneous formation and ensuing propagation of traffic oscillations in congested traffic. By analyzing individual drivers' car-following behavior throughout oscillation cycles it is found that this behavior is consistent across drivers and can be captured by a simple model. The statistical analysis of the model's parameters reveals that driver' behavior during oscillation (i.e., reaction to oscillation) is strongly correlated with driver behavior before oscillations and it varies with the development stage of the oscillation. Simulation of the model shows that it is able to produce characteristics of traffic oscillations consistently with empirical observations. This study also unveils the generation mechanism of the traffic hysteresis phenomenon arising in traffic oscillations using the Asymmetric Behavioral model. It is found that the occurrence of traffic hysteresis is closely correlated with driver behavior when experiencing traffic oscillations. In the growth and fully-developed stage of traffic oscillations, drivers behave differently, which results in different distribution of hysteresis patterns. This research makes it possible to unveil new management and control strategies of traffic oscillations to improve traffic operation and to quantify the environmental and safety impacts of traffic oscillations. For example, it can be used to estimate the increase of greenhouse emission and decrease of fuel efficiency imposed by traffic oscillations. It can also be used to study the increase of accident rate.
12

Adaptive traffic control effect on arterial travel time charateristics

Wu, Seung Kook 16 November 2009 (has links)
An arterial traffic control system influences the travel time characteristics of a corridor, including the average corridor travel time and the travel time reliability. However, reliability measures have typically been outside of the focus of arterial control system performance evaluation studies. To assess the effectiveness of arterial traffic control performance evaluation studies are normally limited to average measures of travel time, speed, or delay. As an advanced traffic management system, adaptive traffic control has been developed to address real time demand variability. Thus, an evaluation of the adaptive traffic control system based on reliability may be as important as evaluation based on average travel time or delay. In addition, arterial control systems may also affect the performance of side street traffic as well as arterial corridor traffic. The performance of side street traffic is another measure that should be used in the assessment of the effectiveness of any arterial traffic control system. Finally, an arterial's operational performance often changes throughout a day and over the arterial length. Thus, a system-wide measure that reflects the range of observed operations is needed to thoroughly assess the performance. Given these issues the goal of this research is the development of procedures to evaluate adaptive traffic control's effect on arterial characteristics such as travel time distribution, reliability, side street performance, and system-wide performance. The developed procedures were applied to the evaluation of an adaptive traffic control system, SCATS (Sydney Coordinated Adaptive Traffic System) in Cobb County, Georgia that replaced a semi-actuated coordinated control system. After the procedures were applied, it was found that SCATS produced a less extreme shape of travel time distribution, possibly due to the adaptive feature, but that it did not make statistically significant changes in the selected overall analysis measures. Also, it was found that the results of the performance evaluation can vary depending on the measures selected or the study period and location.
13

Travel patterns and safety of school children in the eThekwini Municipality

Dhoda, Salma January 2009 (has links)
Submitted in fulfilment of the academic requirements for the degree of Magister Technologiae: Department of Civil Engineering and Surveying, Faculty of Engineering and the Built Environment, Durban University of Technology, 2009. / The annual incidence of pedestrian casualties on South African roads is approximately 34 000. This includes 4 000 deaths, 10 000 serious injuries and 20 000 minor injuries, costing the country an estimated R2,55 billion. A large number of injuries involve children and this is distressing but preventing this is a challenge. Statistics indicate that pedestrians are most at risk. School children have been identified as forming a considerable percentage of pedestrians. Consequently it is important to understand factors that influence children's travel patterns as an initial step toward reducing the accident rate. This study examines children's travel patterns at primary and secondary schools in the eThekwini area. In the absence of statistics regarding journeys to transport children to school, a questionnaire survey was designed to determine demographics, mode of travel to school, travel cost and duration, factors influencing choices of alternate modes of travel and problems experienced during school travel in terms of road safety. In addition, an on-site investigation was undertaken to assess the relevant engineering aspects including geometric design, traffic calming, signage and other traffic management aspects. This study focuses on scholar transport and discusses the findings of pilot and focal surveys. On analyzing the data, various problems were identified, namely: the road environment favours drivers over pedestrians, an absence of a formal travel plan, poor driver behaviour and an absence of dedicated school buses. A range of possible solutions is recommended. The recommendations focus on the Engineering, Enforcement and Evaluation aspects.
14

Travel patterns and safety of school children in the eThekwini Municipality

Dhoda, Salma January 2009 (has links)
Submitted in fulfilment of the academic requirements for the degree of Magister Technologiae: Department of Civil Engineering and Surveying, Faculty of Engineering and the Built Environment, Durban University of Technology, 2009. / The annual incidence of pedestrian casualties on South African roads is approximately 34 000. This includes 4 000 deaths, 10 000 serious injuries and 20 000 minor injuries, costing the country an estimated R2,55 billion. A large number of injuries involve children and this is distressing but preventing this is a challenge. Statistics indicate that pedestrians are most at risk. School children have been identified as forming a considerable percentage of pedestrians. Consequently it is important to understand factors that influence children's travel patterns as an initial step toward reducing the accident rate. This study examines children's travel patterns at primary and secondary schools in the eThekwini area. In the absence of statistics regarding journeys to transport children to school, a questionnaire survey was designed to determine demographics, mode of travel to school, travel cost and duration, factors influencing choices of alternate modes of travel and problems experienced during school travel in terms of road safety. In addition, an on-site investigation was undertaken to assess the relevant engineering aspects including geometric design, traffic calming, signage and other traffic management aspects. This study focuses on scholar transport and discusses the findings of pilot and focal surveys. On analyzing the data, various problems were identified, namely: the road environment favours drivers over pedestrians, an absence of a formal travel plan, poor driver behaviour and an absence of dedicated school buses. A range of possible solutions is recommended. The recommendations focus on the Engineering, Enforcement and Evaluation aspects.

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