Earliest Sensor Detection Opportunity for Left Turn Across Path Opposite Direction Crashes

Left turn across path crashes with a vehicle traveling from the opposite direction (LTAP/OD) are a common and often fatal intersection crash scenario in the U.S. Intersection advanced driver assistance systems (I-ADAS) are active safety systems emerging in the vehicle fleet that are intended to help drivers safely traverse intersections. The objective of this study was to examine the earliest detection opportunity for I-ADAS in LTAP/OD intersection crashes. A total of 35 crashes were extracted for this study's analysis from the NASS/CDS crash database. EDR precrash records taken from each vehicle were then used to determine vehicle position with respect to time. Two scenarios are considered: one with and one without potential sight occlusions. The results suggest that, even if no sight obstructions are present, an I-ADAS that warns drivers of an impending collision will be greatly limited by perception-reaction time. Accordingly, systems that employ automated emergency braking are expected to be substantially more effective. Required detection distances and azimuth values are presented. The results highlight the need for careful tuning of sensor capabilities and the need to consider side-facing sensors for ensuring vehicle tracking prior to any potential collision conflict.