Evaluation of On-ramp Control Algorithms

A freeway corridor consists of the freeway and its entrance/exit ramps, the cross streets, and adjacent parallel arterial streets. It is designed to provide a generally high level of service (LOS) to their users and to the communities which they serve. However, many corridors in the country are congested, with  the  worst  congestion  problems  usually  arising  during  the  two  peak  periods(morning  and  evening)  (Schrank  and  Lomax,  1999).   =There are two types of traffic congestion observed: recurrent and non-recurrent.  Recurrent congestion are due to excessive peak demands and non-recurrent congestion are due to capacity reduction caused by events such as accidents. The control of a traffic corridor, which consists of two major components freeway system control and arterial street system control, is aimed at improving flows on both freeway and arterial streets, and has been demonstrated as an effective mean to increase the level of service of a corridor system during peak periods. Ramp metering, or on-ramp control, which is designed to determine a metering rate for each controlled on-ramp based on traffic conditions of part or whole of the corridor, has been considered a very important component of corridor traffic control.