Congestion is expected to cost the Toronto region up to $15 billion annually by 2031.

But one of the most obvious and unpopular answers to the problem — road tolls, also known as congestion pricing — remains a largely verboten subject in Ontario, even though user fees are already used or under discussion globally.

“I call it the elephant in the road, because for some reason we can’t talk about it,” said Martin Collier.

He’s a founder of the Transport Futures Conference, which will gather an international panel of road pricing experts in Toronto Thursday.

The second annual conference is one sign that, after years of knee-jerk opposition, a serious exploration of the impact of user fees may finally be foisted upon Toronto-area drivers and politicians.