We already trust our robocars
This story from the Register about a test at the Stanford VAIL Lab reports an interesting result. They created a fake robocar, with a human driver hidden in the back. The test subjects then were told they could push the autopilot button and use the car. And they did, immediately picking up their newspapers to read as they would in a taxi (which is what they really were in.)
Not only that, when they were told the robot could not figure out the situation and needed human assist, they gave it, and then went right back to autopilot.
So trust of a robocar is already at a higher level than we might expect. I've ridden in Junior, and K. has stood in front of it, but that was with a human ready to take over the controls. Like many others pondering the future of robotic transportation, I believe we'll only put robocars on our ordinary streets once they demonstrate a level of safety much superior to human drivers what I call the "robocar vision." This does not mean a perfect level of safety, though, and the resulting accidents and occasional fatalities will be the cause of much debate and legal wrangling which will slow the development of the technology when it is saving lives.
Update: You might also like the Cute VW concept video where the dad explains to his son all the strange concepts like petrol, driving, traffic jams, accidents and parking.