However if it is done as each car reacting to what it "sees" I can see some issues with that. For example a fast Audi with 6 piston calipers detects a sudden obstacle (something blown on to the road or some such) anchors up fully. Self driving fiesta behind on budget tyres detects this also applies the brakes fully however doesn't have the same tools at it's disposal, still ends in a crash. Unless it would be programmed to swerve, but that then requires all the cars to talk to each other, stating I'm here doing this I will be in this space shortly etc also the road network itself perhaps as well.
Works well on motorways and predictable roads but I feel as though the technology would have to be truly amazing to deal with all the current variation.