Review of ramp metering methodologies for urban expressway

Abstract

Ramp metering is a viable, reliable and effective strategy which maintains urban expressways in optimum status. Various forms of applications and researches on ramp metering are studied systematically by literature analysis of various countries. It can be classified into different categories according to different control objects, tasks and methods. In view of the history of ramp metering development, a review and analysis is made for the essential urban expressway ramp metering methodologies and their advantages and disadvantages in this paper, which is based on two aspects: isolated ramp metering and coordinated ramp metering. And also some perspectives on the development of ramp metering research are brought up in order to propose the tendency of further studies.