Abstract
Advances in signal controller software and hardware are introducing new safety-enhancing functions to the signal engineer’s toolbox. Hardware-in-the-Loop (HITL) simulation can evaluate alternative timing parameters, detection strategies, and intersection geometries in a safe and cost-effective manner. Red Clearance Extension (RCE) is one design alternative that can be evaluated by HITL simulation. RCE operates by predicting Red Light Running vehicles and dynamically increasing red clearance interval duration to reduce crash probability. In this study, HITL simulation was used to evaluate four alternative RCE detection strategies. Novel code was developed in R to visualize output in Enhanced Time-Space Diagrams (ETSDs). RLR vehicles triggered the highest rate of correct RCE events when the downstream detection alternative was used. However, the ETSDs showed that RCE events triggered by smart upstream speed-conditional detection alternatives at 125, 215, and 475 ft provided greater safety for vehicles with no significant increase to intersection delay incurred.