Full disclosure: This car is perhaps not quite as big as the car you envisioned when you read the headline.
Zheng Wang from Bridgwater State University has used a Raspberry Pi and some other hardware to modify a remote-controlled (RC) car to follow a track, detect, understand and respond to stop signs and traffic lights, and to avoid collisions. Once scaled up and able to do parallel parking, you’ve got something that looks a bit like Google’s self-driving car project. (A bit.)
So what’s happening here? The Pi is hooked up to a Raspberry Pi Camera Module and an ultrasonic sensor. Two client programs on the Pi are used to serve the information it gathers from those devices to another computer over WiFi, with streaming video. The RC controller for the car is given instructions by an Arduino which is hooked up to the computer doing the processing by USB.
Zheng has provided a very detailed writeup, which dives into the maths behind all of this, and provides a look at the neural network on the machine doing the processing.