Browsing by Author "Vairamidis, Nikos"
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Item Development and Application of On-Line, Integrated Control Strategies for Optimal Metering, Incident Management and Driver Guidance in Freeway Networks: Phase I Final Report(1993-04) Stephanedes, Yorgos J.; Kwon, Eil; Chang, Kaikuo; Vairamidis, NikosManaging freeway congestion requires an integrated approach involving demand-responsive ramp metering, incident management and driver guidance. While a freeway network acts as a system, i.e., conditions on any part affect other parts in the network, the state of the art in real-time freeway management has not reached the point where comprehensive, network-wide optimal control schemes are automatically generated and implemented through on-line optimization and coordination of various control actions. A major difficulty lies in the lack of efficient computational algorithms implementable for on-line optimization, and the lack of accurate on-line predictors, that can predict traffic demand and diversion in freeway networks. As a result of the above limitations, most traffic responsive metering systems, such as the Twin Cities freeway control system, employ automatic rate-selection procedures. These procedures select the most appropriate metering rates for a ramp from a pre-determined library using the information received from loop detectors on the main freeway, upstream and downstream from the ramp. Although this method provides a degree of self-adjustment to prevailing traffic conditions, the lack of an efficient analysis tool to evaluate and update the key components of the control, i.e., thresholds and rate-libraries, significantly restricts the effectiveness of control.Item Techniques for Rural Transit Service Design(1991-08) Stephanedes, Yorgos J.; Vairamidis, NikosTransit service is playing an increasingly vital role in maintaining and improving the mobility and economic well-being of rural populations in the North Central region. This has been particularly important as the decline in several small towns has led to a dependency on regional centers or metropolitan areas for services formerly provided locally. While rural transit systems have become more important, higher operating expenses and reduced federal subsidies have made state transit management, design and funding decisions more complex. This project has developed methods and tools to aid these important decisions.