Browsing by Subject "Traffic density"
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Item Development of Algorithms for Travel Time-Based Traffic Signal Timing, Phase I – A Hybrid Extended Kalman Filtering Approach for Traffic Density Estimation along Signalized Arterials(2010-12) Liu, Henry X.; Di, XuanAs technologies continue to mature, the concept of IntelliDrive has gained significant interest. Besides its application on traffic safety, IntelliDrive also has great potential to improve traffic operations. In this context, an interesting question arises: If the trajectories of a small percentage of vehicles (IntelliDrive vehicles) can be measured in real time, how can we use such data to improve traffic management? This research serves as a starting point that aims to produce a paradigm shift to optimize the traffic signal control from the use of the conventional fixed-point loop detector data to the use of mobile vehicle trajectory-based data. Since the change of density on arterials can help traffic engineers to track the queue length at intersections, which is important for traffic signal optimization, in this project we will focus on the estimation of traffic density on urban arterials when trajectories from a small percentage of vehicles are available. Most previous work, however, focuses on freeway density estimation based merely on detector data. In this research, we adopt the MARCOM (Markov Compartment) model developed by Davis and Kang (1994) to describe arterial traffic states. We then implement a hybrid extended Kalman filter to integrate the approximated MARCOM with fixed-point and vehicle-trajectory measurements. We test the proposed model on a single signal link simulated using VisSim. Test results show that the hybrid extended Kalman filter with vehicle-trajectory data can significantly improve density estimation.Item Field Implementation, Testing, and Refinement of Density Based Coordinated Ramp Control Strategy(Center for Transportation Studies, University of Minnesota, 2015-06) Hourdos, John; Geroliminis, Nikolas; Zitzow, Stephen; Limniati, Ypatia StefaniaIn the Twin Cities metropolitan area, freeway ramp metering goes back as early as 1969, when the Minnesota Department of Transportation (MnDOT) first tested ramp metering in an I-35E pilot project. To date, the Twin Cities ramp metering system has grown to include more than 433 ramp meters. Research on better, improved ramp control strategies has continued over the years and MnDOT has implemented minor and major changes in the control logic. Two independent studies both aimed at developing the next generation in ramp metering by focusing on density. Based on these efforts, two new algorithms were developed: the UMN Density and the UMD KAdaptive, named based on the campus at which they were developed. The goal of this project was to implement both algorithms and test them under real conditions. Priorities and technical problems prevented the evaluation of the UMN algorithms, so this report focuses on the evaluation of the UMD KAdaptive algorithm on two freeway corridors in the Twin Cities, MN. The first site, a section of TH-100 northbound between 50th Street and I-394, was selected to compare the then current logic, the Stratified Zone algorithm, with the new one. During the course of this project, the UMD algorithm eventually replaced the Stratified Zone algorithm and was implemented in the entire system. This full deployment also included corridors that were not controlled before. The second evaluation site on eastbound TH-212 was a site that allowed for a with/without control evaluation of the UMD algorithm. This report describes the experiments conducted at both sites and includes a comprehensive review of the state of ramp metering strategies around the world to date.Item Non-linear spacing policy and network analysis for shared-road platooning(Center for Transportation Studies, University of Minnesota, 2019-08) Levin, Michael; Rajamani, Rajesh; Jeon, Woongsun; Chen, Rongsheng; Kang, DiConnected vehicle technology creates new opportunities for obtaining knowledge about the surrounding traffic and using that knowledge to optimize individual vehicle behaviors. This project creates an interdisciplinary group to study vehicle connectivity, and this report discusses three activities of this group. First, we study the problem of traffic state (flows and densities) using position reports from connected vehicles. Even if the market penetration of connected vehicles is limited, speed information can be inverted through the flow-density relationship to estimate space-and time-specific flows and densities. Propagation, according to the kinematic wave theory, is combined with measurements through Kalman filtering. Second, the team studies the problem of cyber-attack communications. Malicious actors could hack the communications to incorrectly report position, speed, or accelerations to induce a collision. By comparing the communications with radar data, the project team develops an analytical method for vehicles using cooperative adaptive cruise control to detect erroneous or malicious data and respond accordingly (by not relying on connectivity for safe following distances). Third, the team considers new spacing policies for cooperative adaptive cruise control and how they would affect city traffic. Due to the computational complexity of microsimulation, the team elects to convert the new spacing policy into a flow-density relationship. A link transmission model is constructed by creating a piecewise linear approximation. Results from dynamic traffic assignment on a city network shows that improvements in capacity reduces delays on freeways, but surprisingly route choice increased congestion for the overall city.Item Safety Impacts of the I-35W Improvements Done Under Minnesota’s Urban Partnership Agreement (UPA) Project(Minnesota Department of Transportation, 2017-06) Davis, Gary A.; Gao, Jingru; Hourdos, JohnAs part of an Urban Partnership Agreement project, the Minnesota Department of Transportation added lanes and began operating a priced dynamic shoulder lane (PDSL) on parts of Interstate 35W. Following the opening of these improvements, the frequency of rear-end crashes increased in certain sections, especially in the PDSL region. The object of this study was to determine if these increases were direct effects of the improvements or were due to changes in traffic conditions. Logistic regression analyses which controlled for changes in traffic conditions indicated no direct effect on the likelihood of rear-end crashes due to operation of the PDSL; the observed change in crash frequency was explained by the change in traffic conditions. This study also found evidence for a nonlinear relationship between a proxy for traffic density, lane occupancy, and the probability of a rear-end crash occurring during an hour. In several sections crashes were most likely when lane occupancies were approximately 20%–30%, and crash likelihood tended to decrease for lane occupancies below and above this range.