Safety and operational impacts of different Autonomous Vehicle operations on freeway work zones

The emergence of new Connected and Autonomous Technology (CAT) has led to significant enhancements in operational efficiency and safety within the realm of transportation. Autonomous Vehicles (AVs) have demonstrated the ability to form platoons, thereby increasing the freeway capacity and reducing fuel consumption. While numerous studies advocate for dedicated lanes for platoons, the transitional phase would encompass mixed traffic conditions and this could decrease safety and operational efficiency on freeways, particularly on sections with work zones and freeway weaving regions. The study conducted safety performance evaluations on an Interstate-80 (I-80) freeway segment. By utilizing the concept of moving work zones and establishing continuous one-mile work zones through the designated segment, the study assessed the impact of work zone placement on vehicle platoons across interchanges and exit ramps. The study particularly made a comparison between two AV behaviors Cooperative AV and AV platooning. To conduct safety evaluations surrogate safety conflict indicator Time to Collision (TTC) was selected and traffic conflicts after the simulations were extracted by utilizing Surrogate Safety Assessment Model (SSAM) tool. Lane change parameters in the simulation platform for human-driven vehicles were updated based on NDS SHRP2 data for clear weather, while those for Cooperative AV and AV platooning scenarios were updated by findings from Co-Exist. While both Cooperative AV and AV platooning scenarios exhibited reduced number of traffic conflicts compared to human-driven counterparts, differences emerged in the types of conflicts. AV platooning scenario exhibited a higher percentage of rear-end conflicts than AV cooperative. By leveraging traffic conflict indicator TTC, this research provided valuable insights for traffic agencies and infrastructure owners and operators (IOOs) to implement work zones safely across different freeway sections within the emerging AV environment.