This recent patent by Lyft, the ride-sharing app, describes a very outgoing autonomous vehicle. The vehicle detects nearby 'entities', e.g., people and cars, and will display different messages to the detected entities based on the situation.
For example, many of us who use Lyft or Uber have been in the situation where we are standing outside a movie theater or airport alongside 20 other people who are also waiting for their hailed ride. Here, the autonomous vehicle can automatically communicate a message to those waiting - this is 'LYDIA'S CAR'. Thus, the message can help ride hailers identify their rides.
Other examples relate to road safety and indicating driving intentions. For example, if the detected entity is a person that is crossing the street, the vehicle may communicate a message that it is 'safe to cross' through a display on the vehicle's windshield.
In another example, if the vehicle detects that the 'entity' is another car and the two cars are at an intersection, the autonomous vehicle may communicate a message that it is 'Yielding'.
Here, the car tells the cyclist that it is 'safe to pass'.
I love this patent because the safety aspect of the patent can help adoption and acceptance of self-driving cars - part of the fear is that it's hard to tell what an autonomous vehicle is 'thinking' whereas, when I'm driving, I tend to look at another driver's eyes or head position to glean their intent. In this case, the message 'safe to pass' indicates to the cyclist that the autonomous vehicle knows where the cyclist is and will let the cyclist pass.