Coordinated Ramp-Metering Control Using a Time-Gap Based Traffic Model

Numerous studies have examined ramp-metering control to relieve highway congestion. Unlike previous research, this paper presents two different optimization problems for maximum system capacity over a highway corridor, using both a time-gap based traffic model describing traffic flow and the limited traffic data measured by existing field facilities. Our proposed algorithms are coordinated ramp-metering controls controlling the metered rates at system-wide entrance ramps. The origin- utilization relationship is taken into consideration in providing the mathematical derivation for the steady-state optimization problem. This scheme regulates on-ramp flows so as to keep traffic densities along the system below their critical densities. To prevent an increase in adjacent street traffic, which might be caused by this scheme, a time-variant linear programming problem is provided with on-ramp queue control and traffic flow estimation. Comparative simulation results for two optimization problems are presented.