The responsible party should be the owner of the vehicle, not the manufacturer or passenger. If a company runs an automated ride share service, for example, that company should be liable. Likewise if you own a car and use the self-driving feature, you are at fault it it goes wrong, so you should use it at your own risk.

That said, for the owner to be truly responsible, they need ownership of the self-driving code, as well as diagnostics for them to be able to monitor it. If they don't have that, do they truly own the car?

That said, there's nothing stopping a manufacturer or dealer from making a deal to cover self-driving fines.