CAREER: Impact of Freeway Geometric Design on Congestion Characteristics

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The objective of this Faculty Early Career Development (CAREER) program award is to establish the relationship between freeway design elements, such as grade and curvature, and traffic congestion characteristics, such as the frequency of stop-and-go movements, hysteresis and capacity drop. The research approach is based on empirical data analysis, both existing and collected as part of this project. Vehicle trajectory data will be used to correlate congestion characteristics and individual driver behavior using a combination of numerical simulations and statistical analyses. This will allow for the unveiling of the link between driver behavior and freeway design, and to propose and validate a car-following theory able to capture the findings in this research. If successful, the results of this research will lead to improved freeway design guidelines, which currently mostly focus on providing adequate capacity. This research will provide answers to questions such as: How should we design freeways so that, when congested, (i) the number of acceleration/deceleration maneuvers is minimized?, or (ii) the bottleneck discharge rate is maximized?, or (iii) the number of lane-changes is minimized? The answer to these questions will potentially help minimize greenhouse gases, commuter delays and accidents, and will promote a more sustainable infrastructure system in the future. Additionally, this research will provide practitioners and researchers with arguably the first traffic flow model able to capture complex congestion phenomena as observed empirically. This will improve the accuracy of existing freeway infrastructure project simulation-based assessments, and will allow testing more efficient congestion control strategies that focus on minimizing emission levels, delays and accidents. The educational and outreach objectives include an on-line portal for promoting traffic flow theory, simulation and modeling, where a community of students, researchers and industry professionals will benefit. This portal includes weekly webinars, data and program tools, a discussion forum and a wiki.