> Does your self-driving car allow the collision and push the offending car back in order to hold your lane? Or does it avoid the collision and run you off the road?
Neiter of those. The first and foremost rule in traffic is to act predicatable. And the only predictable reaction to something blocking your way is to BREAK!
Seriously, what is it always with people that makes them think that a change in direction (swerving) was a good collision avoidcance strategy?
Newsflash, it's not! When swerving you don't change your momentum, you just redirect it (apart from friction losses, of course, the the teensy bit of angular momentum transferred to the planet). More importantly, swerving combined with braking may cause loss of control, which is where there are Anti Break-lock Systems. But ABS will increase your stopping distance, so modern ABS will kick only if the steering wheel does not point into the forward direction.
Of all the scenarios thrown at self driving cars ethics, none of them is an issue if basic traffic rules are followed. And the first and foremost one is, that you always keep so much distance in front of you, that you can come to a full stop within that distance by breaking. And the other first and foremost rule is you never drive faster than road conditions, and more important visibility allow. TL;DR: Don't speed and Don't tailgate!
Any suddenly appearing obstacle in a vehicles way poses the same problem for a human or a computer driver. The computer driver may have the shorter reaction time, but physics is physics and the best course of action remains the same: Braking!