Fundamental Traffic Variables in Adaptive Control and the SCATS DS Parameter

Abstract

This paper discusses the fundamental traffic variables relevant to adaptive traffic control, monitoring and incident detection. The variables considered include headway, gap, occupancy and space times, vehicle spacing, gap length and speed. Speed - flow, spacing - speed, headway - speed, occupancy time - speed and space time- speed functions as well as the relationship between space time and speed as a function of the detection zone length are given. These relationships are based on queue discharge models calibrated using data obtained through surveys in Melbourne. The application of the knowledge about fundamental traffic variables to the estimation of the SCATS DS parameter is presented. The discussion is relevant to the meaning of the basic DS parameter rather than the role of this parameter in actual SCATS operation which is outside the scope of this paper. The analysis and an example demonstrate the soundness of the SCATS DS parameter which is one of the most important parameters in SCATS control.