Further to NeilT's insightful
Further to NeilT's insightful comment, the other major - possibly the biggest - issue is getting human beings to accept that a machine is never going to be perfect, no matter how good it is. Witness the person (I'm not going to name hm as that would be a tacit support for his loony position) running for senate (FCOL!) who is so blinkered to the very obvious potential benefits of autonomous cars in general and Tesla's efforts specifically that he is basing his entire campaign on an anti-autonomus vehicle theme. I'm guessing he is so ignorant that he has never even once considered how many lives Tesla's Autopilot has already saved every time we've seen yet another instance of a Tesla driver unconscious (for whatever reason) behind the wheel of their car doing 70mph down a highway - something that happens in the vehicle world thousands of times every single day. On that basis alone, Autopilot has certainly saved many more lives, injuries and general road-carnage than it has ever caused (which is zero in my book if you consider it is only supposed to be a driver assistance system and not a fully autonomous one).