The coming age of lorries that drive themselves or robots that perform surgery is fraught with legal and ethical issues, says a new report.
The Royal Academy of Engineering says that automated freight transport could be on the roads in just 10 years' time.
Also, it says, robotic surgery will begin to need less human intervention.
But it suggests that much debate is needed to address the ethical and legal issues raised by putting responsibility in the hands of machines.
"We're all used to automatic systems - lifts, washing machines. We're talking about levels above that," said Lambert Dopping-Heppenstal of the Academy's engineering ethics working group.
"It's about systems that have some level of self-determination."
Issues surrounding autonomous systems and robots with such self-determination have been discussed for a number years, particularly with regard to the autonomous machines of warfare .
However, the era of autonomous road vehicles and surgeons is slowly becoming reality, making the issues more urgent, the report says.
The removal of direct control from a car's driver is already happening, with anti-lock braking systems and even automatic parking systems becoming commonplace.
But the next step is moving toward completely driverless road vehicles, which already exist in a number of contexts, including London's Heathrow Airport.
The Darpa Grand Challenge, a contest sponsored by the US defence department's research arm, has driverless cars negotiating traffic and obstacles and obeying traffic rules over courses nearly 100km long.
"Those machines would have passed the California driving test, more than I would have," said Professor Will Stewart, a fellow of the Academy.
"Autonomous vehicles will be safer. One of the compelling arguments for them is that the machine cannot have an argument with its wife; it can run 24 hours a day without getting tired. But it is making decisions on its own."
Professor Stewart and report co-author Chris Elliott remain convinced that autonomous systems will prove, on average, to be better surgeons and better lorry drivers than humans are.
But when they are not, it could lead to a legal morass, they said.
"If a robot surgeon is actually better than a human one, most times you're going to be better off with a robot surgeon," Dr Elliott said. "But occasionally it might do something that a human being would never be so stupid as to do."
Professor Stewart concluded: "It is fundamentally a big issue that we think the public ought to think through before we start trying to imprison a truck."