Book excerpt: An increasing number of automated vehicles will pervade our traffic systems in the future. The absence of a human driver requires these vehicles to communicate to, and interact with other traffic participants, such as vulnerable road users (pedestrians, cyclists, and emerging mobility forms like eBikes or scooters), but potentially also drivers of manual vehicles. In this regard, various studies and concepts demonstrating so-called “external Human-Machine Interfaces” (eHMIs) have been presented in the past couple of years. Many of these works have investigated comparably simple scenarios, such as a single pedestrian aiming to cross the street when an automated vehicle is approaching. Although we still welcome such contributions, research in this area will have to take more complex situations into account. This drives the need for research addressing other situations involving groups of vulnerable road users and traffic participants, different scenarios including roundabouts or urban shared spaces, but also exploring the potential of communication and interaction beyond such classical situations to improve cooperation in traffic.