TORONTO -- It's the ethical decisions made behind the wheel -- and not technological hurdles -- that will pose one of the most difficult challenges to automakers assembling self-driving cars, a senior Audi executive said Friday.

Markus Auerbach, who heads up the Audi Innovation Research office in San Francisco, said developing self-driving technology is only one component of the shift towards autonomous driving.

The bigger challenge will be the ethical decisions that robots will have to make while driving, Auerbach said.

He cited the following example: an autonomous vehicle that can't avoid a collision could be forced to choose between hitting a child who is crossing the street and an elderly woman on a bike.

"A car, out of control, is a weapon," Auerbach said during a panel at the Canadian International AutoShow in Toronto.

The machines that control the vehicles will need a framework to make decisions in such cases, and that means society will have to confront some difficult ethical issues, Auerbach said.

The Ontario government announced last fall that it will allow for self-driving cars to be tested on its roads starting this year.

Economic Development Minister Brad Duguid said Friday that the province's goal is to become "one of the easiest places on the planet" for automakers to conduct research on technologies such as autonomous driving and electric vehicles.