It's a combination of sensors and AI. You'd be surprised by how low quality (wrt framerate & resolution specifically) the sensors used in production autonomous features/vehicles are.
See mobile-eye's papers and products: http://www.mobileye.com/wp-content/uploads/2011/09/StereoAss...
The newest reference date in that paper is 2009 so I suspect the paper itself is a bit old. I really doubt that video would be other than state-of-the-art when the whole system is so expensive.
Edit: Also that company makes add-on collision detection products. That is a different application than auto-driving.
I worked on these cars this summer at GM. I can't say what model of camera sensors we used for obvious reasons, but the resolution and framerate were not too far off from what Mobileye has in that paper!
Edit: Also that company makes add-on collision detection products. That is a different application than auto-driving.