Actuated Traffic Signal Control at Diamond Interchange

The traffic experimental and analytical simulation (TEXAS) model for intersection traffic, version 3.0 was used to simulate actuated signal control and traffic response at a diamond interchange with representative geometric features. Graeco‐Latin Square and one‐way analysis of variance experimental techniques were applied to investigate the effects of various actuated traffic signal controller settings under three different traffic demand conditions—two symmetrical, and one lopsided. Overall average total delay and stop delay for vehicles traveling through the simulated interchange area were used as the response variables in the statistical analysis and significance testing of data obtained from more than 2,500 runs of the TEXAS model. Results indicated that the settings of the timers that determine clearance‐green, green‐split, and end‐of‐maximum intervals on actuated diamond‐interchange signal controllers were sensitive to both intersection geometry and traffic demand and played a significant role in defining the optimum controller settings when implementing a three‐phase, lag‐lag phase‐sequence pattern. Findings from the study of a four‐phase‐with‐two‐overlaps, lead‐lead phasing pattern indicated that the advanced green timer and the internal detector logic were the only controller settings that had a significant effect on traffic performance for the conditions studied. The TEXAS model, version 3.0 is a powerful new analysis tool for determining the best signal timing at individual diamond interchanges operating under specific traffic, geometry, and control conditions; this study illustrates its application.