Re: Sounds rather flawed to me
The idea that someone has to maintain their car (including software) properly is just extending the MOT process to include software and patching.
Wrong analogy. Software does not degrade through use like hardware. Network connected devices need software updates to guard against network-borne attacks. Non-networked devices only need software updates to fix bugs that affect their operation (or changes to their operating environment).
If software updates are legally required for non-networked devices, that would be a legal admission that the old code was not fit for purpose - the software equivalent of a product recall. In this case, the software vendor would then become liable for past accidents involving vehicles that ran the old code. To avoid such liability, the software vendor cannot admit that the old code is unsafe, just less efficient or less functional.
If vehicles had to run the latest code by law, your car would not allow you to start a journey until it had checked for updates. Also it would have to maintain constant network access while driving to stay up to date. The moment a bug is reported in the code, to avoid liability they would have to transmit a network message to halt all vehicles until a fix has been produced, and downloaded to your vehicle.
To maximise road safety, computers must control the whole environment - i.e. human drivers, cyclists, and maybe pedestrians are prevented from using the road. To attain this they may use soft methods like artificially increased insurance premiums for human drivers, despite there being no inherent reason why human drivers should be more dangerous (write off more value + cause more injuries / fatalities) than than at present. A free market for insurers would keep premiums for human drivers comparable to what they are now.
However when accidents occur between human drivers v self-driving vehicles, drivers will be in opposition with corporate lawyers so are more likely to lose legal cases. That said, corporate lawyers may deliberately accept liability at first to win public support, then turn up the pressure when there are few human drivers left on the road.