To me the question is relatively uninteresting because it seems obvious.
As long as cars belong to individuals they have the responsibility to favor the interests of those individuals as far as law permits. Where and how much the community is to be preferred over the individual, the community should specify in laws. People running code that breaks those laws should be liable for that codes actions. (I could imagine an ethics slider settable at the owners choice within the legal limits that allows them to discount the lives of the passengers compared to the lives of others, on the condition that they notify their other passengers).
It's possible that ultimately the right choice is to move to a different model, but in that case, the AI should not be owned by the individual who bought the car and has a reasonable expectation that it work on their behalf.
The ethical decision on the car is no different than the ethical decision that we ask the human driver to make in similar situations (which as the gp noted are incredibly rare), or that we trust the human driver to make when we are passengers in their car. In fact I even doubt that it makes sense to legislate it, since we haven't so far for e.g. uber drivers, but perhaps testing will indicate that we should.
In terms of the speed limits, society has already decided to accept a huge number of deaths per year that would almost all be preventable with a speed limit of 35mph, so I don't see how the introduction of AI drivers affects this question.
I would like to see laws that say that all source code for self driving cars must be publicly auditable and pass tests before being approved for road use. Running code that has not been safety tested by the state will leave you uninsurable and personally liable for its actions. We should aim to make running the test suite as accessible as possible in order to allow innovation, but it should still give us a high confidence that the driver behaves correctly according to the law.
I take pretty much all of this from analogy with human drivers: when we're driven by someone else, we have relatively little control over their ethical slider setting, we have high speed limits for humans because we think the convenience of the many is more important than the lives of the few, we don't let brand new humans drive without having some indication that they'll make the right decisions. None of these problems seem to be particularly changed by the introduction of AI.