Optimal Freeway Ramp Control without Origin-Destination Information

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Optimal Freeway Ramp Control without Origin-Destination Information

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This paper develops an analytical framework for ramp metering, under which various ramp control strategies can be viewed as ramifications of the same most-efficient control logic with different threshold values, control methods, and equity considerations. The most-efficient control logic only meters the entrance ramps nearest critical freeway mainline sections so as to eliminate freeway internal queues, which is derived from a new formulation of the optimal ramp control problem. Instead of assuming the availability of real-time origin-destination information, the new formulation takes advantages of the stability and predictability of off-ramp exit percentages. Those properties of the off-ramp exit percentages are supported by empirical data, and allow us to formulate the optimal ramp control problem as a linear program whose input variables are all directly measurable by detectors in real-time. The solution is also tested on a real-world freeway section in a microscopic traffic simulator for demonstration. Time-dependent origin/destination tables and off-ramp exit percentages are compared as two alternative ways to represent the true real-time demand patterns that are important to freeway ramp metering.


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Minnesota Department of Transportation

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Zhang, Lei and David Levinson (2004b) Optimal Freeway Ramp Control without Origin-Destination Information. Transportation Research part B 38(10) 869-887.

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Zhang, Lei; Levinson, David M. (2004). Optimal Freeway Ramp Control without Origin-Destination Information. Retrieved from the University Digital Conservancy, http://dx.doi.org/doi:10.1016/j.trb.2003.11.003.

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