SIMULATION MODELLING OF PERMITTED LEFT-TURN SATURATION FLOW RATE BASED ON OPPOSING THROUGH-FLOW DEGREE OF SATURATION

This paper presents the modelling of the saturation flow rate of the permitted left turn in an exclusive lane. In the proposed model, the total permitted left-turn saturation flow rate is determined as a sum of saturation flow rates during the effective green time and the intergreen period. Primarily, the permitted left-turn saturation flow rate during the effective green time is modelled based on the opposing through-flow degree of saturation and the number of opposing through flow lanes. The relation between the permitted left-turn saturation flow during the effective green time and these variables was examined using data from the simulation experiments in VISSIM. To our knowledge, this is the first study of the permitted left-turn saturation flow modelling based on the opposing through-flow degree of saturation instead of the opposing through-flow rate and signal-timing parameters. The proposed model was validated based on data collected at seven intersections with a permitted left turn served in an exclusive lane. The permitted left turn saturation flow rate could be accurately determined based on the opposing through flow degree of saturation and the number of opposing lanes according to the RAISE of 58.4 pcu/h.