The kind of lawsuits you'd possibly see due to a faulty computer system causing traffic accidents and possibly deaths due to those accidents would cause such a debacle over their use. That's the main reason why I don't think you'd see them used, let alone made legal, anytime soon.

Like everything else, the technology will have to be proven safe before it is even considered. The closest we are right now to this is more like computer assisted driving, which includes things such as navigational aids and collision alarms. But the human driver is still the one in control of everything.