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Browsing by Author "Ambadipudi, Ravi"

Now showing 1 - 3 of 3
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    Capacity Analysis for Dynamic Bottlenecks and Alternative Concepts for Coordinated Ramp Metering Operations
    (2001-12-01) Kwon, Eil; Nanduri, Sreemanaraya; Ambadipudi, Ravi
    This project involved a detailed review of coordinated metering algorithms currently operating in the United States and a simulation analysis to examine the performance of three algorithms that represent each coordination approach; the Denver incremental coordination, the Seattle Fuzzy metering, and the Minnesota explicit section-wide coordination approaches. Researchers used a macroscopic simulation model with the same geometry and traffic demand conditions. Based on the analysis results, they developed alternative metering approaches by combining conventional zone-wide control with fuzzy coordination. They also developed two new alternative procedures to estimate bottleneck capacities in real time; an adaptive estimation method using Kaman Filter and a neural-network based approach that predicts traffic volume for a given mainline location using traffic data collected from upstream and downstream detectors. Both approaches were tested with the real data collected from the sample freeway sites. The preliminary test for alternative strategies using simulation with an example freeway in Minnesota showed promising results in terms of reducing congestion and increasing throughput on the mainline. Further testing and research is recommended.
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    I-494 Future Improvements Evaluation with Two Traffic Simulators
    (2005-05-01) Xiao, Haifeng; Ambadipudi, Ravi; Hourdakis, John; Michalopoulos, Panos
    In anticipation of increased traffic, many transportation agencies endeavor to redesign traffic networks to improve operational efficiency. These agencies frequently employ the strategy of increasing overall capacity. Field-testing for predicted outcomes of these improvements is usually unwieldy and inaccurate. Increasingly, highway design professionals depend on the use of simulation models to predict the consequences of their proposals. The primary advantage of simulation models in the analysis of a complex system is that models are capable of capturing the interactive effects of different components in the system. These authors have evaluated a proposed redesign of a section of the I-494 corridor using two state-of-the-art microscopic simulators: AIMSUN and VISSIM. Results are compared by assessing differences in the outcomes of the two systems and an assessment as to whether they result in similar or measurably different conclusions.
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    Methodology for Selecting Microscopic Simulators: Comparative Evaluation of AIMSUN and VISSIM
    (2005-05-01) Xiao, Haifeng; Ambadipudi, Ravi; Hourdakis, John; Michalopoulos, Panos
    Because federal regulations require that all changes to existing traffic systems be checked for operational efficiency, simulation models are becoming popular evaluation tools. There are several highly regarded simulation models available. However, there are no guidelines for selecting a simulator that is most suitable for meeting the needs of a specific project. The authors present a simulation model selection process that takes into account quantitative and qualitative criteria. The qualitative evaluation process includes functional capabilities, input/output features, ease of use and quality of service. Quantitative evaluation considerations include accuracy, completion efforts and the parameters involved. They also present a grading scheme in order to reduce subjectivity in the evaluation process. For demonstration purposes, the authors used AIMSUN and VISSIM systems to model a real freeway section and compiled the evaluation results.