Volume-Occupancy-Based Actuated Signal Control System: Design and Implementation to Diamond Interchanges in Houston

This paper presents a new volume-occupancy-based actuated signal control system for a diamond interchange, where a two-way arterial street intersects two one-way streets on each side of a freeway, aiming to approximately capture vehicle platoons and thus to improve the traffic by adaptively adjusting the plan. As a sponsored project aiming at immediate implementation, this system had to be designed based on conventional loop detectors and Econolite ASC/3-2100 Controller, which are currently used by the Texas Department of Transportation (TxDOT). Loop detectors placed in the pavement at each approach were used to collect real-time traffic volume and occupancy every 1 min. These data were then aggregated into 15-min flow and 15-min average occupancy, used in the proposed control logic to help vehicle platoons more smoothly passing through a diamond interchange. Based on onsite observations and data from loop detectors, it shows that the proposed system works well when the traffic flow is higher than 400 veh/h/ln. For arterial roads in the morning peak hours, the occupancy can be reduced by over 10% with a similar or even higher flow rate. The findings exhibit a low-cost method to improve traffic flow at a diamond interchange by using widely used conventional loop detectors.