Download or read book Characterizing Uncontrolled Traffic Conditions in Postwar Beirut written by Ghassan Najib Alam and published by . This book was released on 1997 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since geometric features of urban roadway networks constitute a somew hat fixed parameter, studies aiming at improving urban traffic flow are mostly concerned with enhancing features dealing with operational aspects, namely, traffic control. The extent of traffic control has been addressed using many probabilistic theories trying to optimize the performance of networks given several variables. This thesis presents an attempt to investigate the quality of traffic service under mostly uncontrolled conditions. A framework for analysis is provided by the urban road network in the city of Beirut in the period after 17 years of war. At the microscopic level, the operation of intersections w ith moderate traffic volumes under uncontrolled conditions is characterized using measures such as delays, throughput, and conflicts. The performance of such intersections under other types of control is evaluated and compared with observed measures, and the tradeoffs are identified. A simple simulation model is developed as a proof of concept. The shift from the microscopic to the macroscopic level is accomplished through a travel time survey, which provides a wider picture combining intersections and street segments. The next level is the network level. A useful tool to characterize traffic at this level is the two-fluid model: the two fluids consist of moving and stopped vehicles as a result of traffic conditions, and their interaction is observed to produce several parameters contributing to the scope of this research. This model also provides the mean to perform a sensitivity analysis whose objective is to evaluate the impact of introducing several control measures in a context characterized by lack of control. The study indicates that while lack of control may result in lower delays at intersections for certain levels of traffic volumes, this occurs at the expense of potential safety risks and reflects aggressive driving practices: the potential instability in uncontrolled intersection performance as aggressive driving levels and traffic volumes increase necessitate the implementation of traffic control measures. A similar conclusion is reached using urban-level traffic models: Implementation of traffic control measures in situations characterized by lack of control w ill yield lower delays at high levels of traffic concentrations.