A Contract-Based Design Methodology for Safety in Autonomous Vehicles

The present-day technological advancements in the domain of autonomous vehicles (AVs) claim diversified benefits in terms of safety, reliability, and reduced rate of accidents. Providing safety guarantees for all AVs without exception in all possible situations is considered to be of paramount importance for the successful deployment of AVs on the road. The application of formal verification methods is suggested in this context to guarantee the safety of AVs. Therefore, these methods are computationally incompliant especially in the case of complex systems due to multitudinous interactive components specifically. Keeping this context in mind we have proposed an Assume/Guarantee (A/G)-based contract methodology for guaranteeing the safety of AVs. Our preeminent objective is to avoid collision between AVs during overtaking maneuvers by providing rigorous safety guarantees using Contract-Based Design (CBD). Our approach comprises the following steps: 1. formal specification of basic and updated, A/G contracts based on collision-specified scenarios, 2. creation of collision-based scenarios in CARLA scenic for testing the validity of the proposed approach, 3. implementation of scenario-oriented controller implementing A/G contracts referred as scenario oriented contracts, 4. testing of controller implementing basic and updated A/G contracts with the help of simulation performed in CARLA Scenic while considering the defined collision oriented scenarios. The first step followed in our proposed methodology for the safe overtaking maneuver of AVs is the implementation of basic A/G contracts covering existing speed limits: the maximum speed limit for AV is 60km/h. These basic A/G contracts are replaced by updated A/G-based contracts covering relaxed speed limits: the maximum speed limit for AV is 130km/h when the AV has a risk of collision. The proposed methodology leverages the A/G contracts and shows adequate results by proving that the CBD can provide a propitious road map for guaranteeing the safety of AVs during overtaking maneuvers.