Abstract Contracts to Ensure Safe Traffic Environments Surrounding Automated Vehicles

Abstract

This paper suggests definitions of consistent priorities among automated vehicles and surrounding mobility systems as abstract contracts using laws in order to ensure the safe traffic environments. Behaviors keeping the priorities in the abstract contracts support automated vehicles and their surroundings to avoid occurrence of deadlocks. Automated vehicles including embedded software systems are required to interact with other independent systems such as pedestrians and other vehicles. However, unless the basic conventions about decision-making and behaviors for them are defined, automated vehicles behavior may cause deadlocks among constituent systems. Deadlocks can be hazard sources that surrounding mobility systems cause traffic accidents or emergency vehicles cannot achieve their purposes. Therefore, automated vehicles and surrounding systems should avoid deadlocks to reach safe environments minimizing harms. To address these issues, abstract contracts should be defined before concrete design stage of automated vehicles. In this paper, first, whole traffic environments including automated vehicles are regarded as a “System of Systems” involving automated vehicles. Second, priority relations are set for each pair of constituent systems. Then, the rankings about priorities are calculated with pairwise approaches. We use three different methods to compare the rankings. It is shown from the priority rankings that there are possibilities for automated vehicles to cause deadlocks in traffic environments due to their different decisions. Moreover, we consider the influences caused by the differences of laws using Japan and the State of California as sample scenarios.