Browsing by Subject "Bottlenecks"

Now showing 1 - 4 of 4
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    Development of Active Traffic Management Strategies for Minnesota Freeway Corridors
    (Minnesota Department of Transportation, 2015-06) Kwon, Eil; Park, Chongmyung
    In this study, the effectiveness of the I-35W variable advisory speed limit system on the improvement of the traffic flow was evaluated with the real traffic data. The analysis results indicate there was significant reduction in the average maximum deceleration and also the traffic time reliability was substantially improved during a peak hour period. Based on the assessment results, an enhanced version was developed to be able to reflect more effectively the time-variant road traffic conditions in determining the variable speed limits in real time. The coordinated adaptive metering strategy, developed in the previous phase of this research, is also enhanced and implemented in the field in this research. The field test results of the new metering system with the 100 NB corridor indicate substantial improvements in both the mainline and ramp traffic performance compared with those from the old stratified algorithm.
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    Enhancing Performance Evaluation and Characterization Techniques to I dentify Performance Changes in High-Performance Computing Systems
    (2021-11) huerta, yectli
    High Performance Computing systems are complex and require a lot of effort to tune the system to achieve peak performance. Performance analysis is a time consuming process. The goal of this thesis is to understand the effects changes to the system or compiler configuration had on performance and how it is reflected in CPU performance metrics. This thesis presents two approaches to enhance the evaluation process of HPC systems. First, a process that makes it possible to systematically and efficiently search the parameter space to find an optimal configuration of a benchmark with a large number of tunable parameters is introduced. The search for an optimal combination of parameters can be daunting, especially when it involves high dimensionality of mixed type categorical and continuous variables. This thesis shows that through the use of statistical techniques, a systematic and efficient search of the parameter space can be conducted. These techniques can be applied to variables that are categorical or continuous in nature and do not rely on the standard assumptions of linear models, namely that the response variable can be described as a linear combination of the regression coefficients. Second, a normalization technique that will make it possible to identify relative differences between performance metrics to better understand the effects changes had on the underlying system is presented. The use of Top-Down microarchitecture analysis method makes it possible to understand how pipeline bottlenecks were affected by changes in the system configuration, or compiler version. Bottleneck analysis makes it possible to better understand how different hardware resources are being utilized, highlighting portions of the CPU's pipeline where possible improvements could be achieved. The Top-Down analysis method is complemented with the use a normalization technique from the field of economics, purchasing power parity (PPP), to better understand the relative difference between changes. This thesis showed that system changes had effects that sometimes were not reflected on the corresponding Top-Down metrics. The use of the PPP normalization technique made it possible to highlight differences and trends in bottleneck metrics, differences that standard techniques based in absolute, non-normalized, metrics failed to highlight.
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    Improving intersection safety through variable speed limits for connected vehicles
    (Center for Transportation Studies, University of Minnesota, 2019-05) Levin, Michael; Chen, Rongsheng; Liao, Chen-Fu; Zhang, Tab
    Autonomous vehicles create new opportunities for innovative intelligent traffic systems. Variable speed limits, which is a speed management systems that can adjust the speed limit according to traffic condition or predefined speed control algorithm on different road segments, can be better implemented with the cooperation of autonomous vehicles. These compliant vehicles can automatically follow speed limits. However, non-compliant vehicles will attempt to pass the moving bottleneck created by the compliant vehicle. This project builds a multi-class cell transmission model to represent the relation between traffic flow parameters. This model can calculate flows of both compliant and non-compliant vehicles. An algorithm is proposed to calculate variable speed limits for each cell of the cell transmission model. This control algorithm is designed to reduce the stop-and-go behavior of vehicles at traffic signals. Simulation is used to test the effects of VSLs on an example network. The result shows that VSL is effective at reducing the energy consumption of the whole system and reduce the likelihood of crash occurrence.
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    Prioritization of Freeway Segments Based on Travel Time Reliability and Congestion Severity
    (2017-06) Biswas, Rudrakshi
    Improving road geometry to mitigate congestion within a given budget is a constant challenge for state agencies. It is important to prioritize among different projects to serve the need in the best possible way. Bottlenecks on freeways affect travel time reliability and congestion. Many prioritization methods have been developed to rank bottlenecks based on congestion. No existing research has tried to combine both travel time reliability and congestion to capture the effects of bottlenecks on freeways. A new index, vulnerability index, is developed combining buffer index and 95th percentile travel rate. This index reflects the effects of travel time reliability and congestion severity. Buffer index indicates the variability of travel time and 95th percentile travel rate indicates the congestion of the freeway. Interrelationships between buffer index and 95th percentile travel rate have also been analyzed. Two approaches (i.e. yearly data analysis, daily data analysis) have been used in estimating travel time reliability and congestion indices. Three prioritization methods have been proposed. One approach uses the yearly data, while the other approaches use the daily data to rank the freeway segments. US 169 NB and SB corridor has been used as the study corridors. Each corridor is segmented into three segments each, and the travel time reliability and congestion severity measures were estimated for each segment. The new prioritization methods are then applied to these segments, whose priorities were determined with the value of vulnerability index.