OPTIMAL RAMP-METERING CONTROL FOR FREEWAY CORRIDORS

The paper discusses an optimal ramp-metering control model wherein a corridor is discretized into small road sections, with density as the state variable and ramp metering rates, the control variables. In each section the density dynamics are estimated by a continuum model developed with the conservation equation, and formulated as a state equation. The optimization process adjusts the metering rate of each ramp according to corridor traffic conditions such that the total corridor travel time during a certain period is minimum. The paper also presents a test of the optimal metering for a simple one-entrance-ramp segment of the freeway corridor. Fixed signal timing, upstream demands, diversion rates, turning percentages, and initial densities are known and the optimization period is three minutes.