A Comparative Safety Performance Evaluation of Automated Driving Systems and Advanced Driver Assistance Systems

Vehicles with automated driving systems (ADS) and those with advanced driver assistance systems (Level 2 ADAS) operate in various locations in the US. The Federal Highway Administration (FHWA) has collected crash data for ADS and Level 2 ADAS–equipped vehicles. Understanding the safety benefits of these highly automated vehicles would provide the FHWA insights and guidance on improving their safety. Thus, this study applied Bayesian networks to evaluate the severity of ADS and Level 2 ADAS–involved crashes. Specifically, the study intends to determine the safety benefits of ADS over Level 2 ADAS in various traffic and roadway conditions. Two models focused on different categories of injury severity scale (KABCO) were developed. Results indicated that, overall, ADS-involved crashes are relatively less severe compared with Level 2 ADAS–involved crashes. On average, the probability of KA and KABC crashes is about 12% and 11% lower for ADS-equipped vehicles than Level 2 ADAS–equipped vehicles. The safety assessment across various roadway facilities, traffic conditions, and environmental factors showed relatively similar performance of ADS and Level 2 ADAS for KABC and KA crashes. Higher safety benefits of ADS-equipped vehicles were observed at low-speed limit roadways, clear weather, and intersections, among others. On the other hand, the safety performance of ADS-equipped vehicles deteriorates on the freeway, especially at 96 km/h (60 mi/h) and above. Overall, the findings suggest that most cases of ADS-equipped vehicle crashes are relatively less severe. These findings may be crucial to safety practitioners and planners focusing on deploying ADS-equipped vehicles on their roadway networks.