Freeway Traffic Control and Surveillance Model

The development of on ramp metering control strategies for a freeway can be aided by the well-developed theory of linear optimal control. The recently developed aggregate variable model appears to be best suited for this purpose. In this model the freeway is partitioned into lengths of about 1/2 mile and traffic is described in terms of the aggregate variables section speed, section density, and volume. This model and linear optimal control theory are used to develop an on ramp metering strategy which is designed to maintain freeway conditions near nominal conditions in the presence of disturbances. An illustrative design for a segment of the San Diego freeway in Los Angeles is provided. The companion problem of processing freeway sensor data to provide current estimates of the aggregate variables can be approached through standard techniques in estimation theory. Methods of attacking this portion of the freeway surveillance problem are presented.