To be honest, I don't see the likelihood of a fully autonomous car becoming a mainstream in the "near" future. Its not about the technology, but it is the trust in technology which is the biggest hurdle. Instead of autonomous cars they should start with autonomous trains, buses, long haul trucks (with dedicated route), quadcopters for transport (distant future),  just to build trust. Then they should use it as a driver assist kind of feature in emergency situation. Finally when enough trust is built, they should start testing it in passenger cars for a completely handoff kinda Autopilot.