Computer failure is my thought due to corrosion. Software failures Rust belt area driverless cars would be most prone. But you're right. Solution would be water tight boxes for the computers (already the case). It will get sorted out though. You are correct. It's going to be a brave new world. Even more highly regulated I believe. We can revel in the fact that we are at the tail end of the art of driving and the freedoms associated therewith.
Richard E.
As an addendum, most accidents are the result of driver error versus mechanical failure so driverless cars are a coming in full force.