Green Extension and Traffic Detection Schemes at Signalized Intersections

Abstract

This paper provides analyses of green extensions associated with two vehicle detection schemes for actuated signal control: the current single-channel detection and the emerging lane-by-lane detection. The current single-channel detection has all detectors across all lanes on a particular approach providing a single input to a signal phase. Lane-by-lane detection, however, monitors headways and gaps on a lane-by-lane basis. A simulation model was developed to analyze both detection schemes. With the simulation model, green extensions by the two detection schemes were compared over a wide range of traffic scenarios. On the basis of study results, it was found that the two detection schemes do not produce significantly different green extensions under normal traffic flow conditions. For the various factors examined, maximum allowable headway (also passage time) is found to be more sensitive compared with other factors such as arrival headway patterns and lane volume distribution. Although the difference between the two detection schemes in average green extension is generally minimal, large differences do exist among certain cycles, and the actual impact on signal operations could be more significant; this would need further evaluation with other standard traffic simulation models.