On a serious note, I firmly believe that driveless cars will *never* be truly workable in the current real-world environment until/unless artificial intelligence makes some big breakthroughs. Philphine brings up a great point about the driverless car figuring out if a motorcycle or other smaller object is occupying a lane. Without really awesome (and not-yet-attained) AI, any attempt to handle these sorts of situations individually are just limited-scenario hacks.
Matt