This study presents an analysis of the interaction between a driver and an automated driving system (ADS) using a communicating sequential process (CSP). Level 3 of automated vehicles requires that drivers are able to take control from the ADS in emergency situations. To allow this, the interactions between the driver and ADS must be treated as part of the safety system. In an emergency situation, the ADS must know the driver's current state, to judge whether to hand over control of driving. If the ADS cannot monitor this successfully, the driver may be inappropriately given control of the vehicle. In this study, the driver and the ADS were treated as a concurrent system in a system of systems, in which both operated independently, while interacting through a human machine interface. A CSP model was built to describe the interactions between them, and these were analyzed using model checking. The CSP model was based on analysis using System Modeling Language. A simple four-stage model of human information processing was used to describe the driver's state transitions. The study contributes to the analysis of the interactions between an ADS and the behavior of a driver, and will help designers of automated vehicles.