Actually with driverless vehicles, the main risk is not from the police but from malicious people hacking into the car's systems and crashing it to show how "clever" they are.

The thing is that the cars will, legally, end up in the hands of civilians with the powers of the police. Thus anybody who has ever been "naughty"* in a taxi ever may well end up being arrested. Not saying it will happen but the ridiculous anti-pornography laws in this country weren't something I would imagine happening anywhere outside of an Emirate.
I agree though that, at least in the physical harm to the innocent stakes, people cracking the systems and taking control to create mayhem could be a bigger threat.

*depending upon how law is interpreted an awful lot of conversations fall under this especially if they're legally being overheard by a third party.

Using the same logic, the WWW should probably have not been invented.

The "internet of things" probably poses greater risks, or at least equal risks - driverless vehicles being just one aspect as whether driverless or not, connected vehicles could be vulnerable to attackers.

So long as a physical override exists, the threat is lessened significantly, take away that and abandon all hope.

edit
https://www.eff.org/deeplinks/2016/0...hat-it-used-be

Not exactly the same things.
The Internet can't physically kill you in a couple of seconds or detain you on the whim of some "security consultant" who decides they don't like what you are doing or saying.
This is not to say that I disagree with the premise of automated vehicles entirely -- just that they are a lot more acutely dangerous than even a dodgy heating or electrical system.

The reason I argue for owner responsibility for the actions of such devices is that corporation are never held accountable for their actions and never suffer consequences since they are non-existent pseudo-people, modelled upon psychopaths, intended to make money. They are, therefore, unpublishable hence a lot of the world's problems. Sadly, of course, corporations will just own these vehicles and, therefore, will be given carte-blanche to kill whomever they feel like "by mistake" (look at The Metropolitan Police, PLC for examples).