The biggest transportation plan in Southern Ontario's history failed to recommend road tolls as a way to pay for billions in needed transit improvements.

But if the absence of tolls from Metrolinx's $50 billion transit expansion plan suggests the idea is dead, nobody told the 125 people, including almost two dozen from the provincial government, who packed a one-day conference in Toronto last week.

With only $11.5 billion dollars committed for the plan so far, by the province, the question of where the other $38.5 billion will come from looms large.

Metrolinx chair and former Burlington mayor Rob MacIsaac reiterated as recently as the weekend that the idea of a road toll or other tax will be easier to sell publicly once transit and other improvements are in place.

A 10-cent-per-kilometre charge on the QEW from Hamilton to Toronto, for example, would cost a commuter about $260 a month.

But observers like Trent University economics professor Harry Kitchen maintain it's not a matter of if we'll see road tolls, it's when.

Municipalities need new ways to pay for aging infrastructure. His research suggests tolls are among the fairest ways of doing that.

"I think it's inevitable; road tolls are going to come," said Kitchen. "The really critical issue in the Greater Toronto Area is that there's got to be some additional financing specifically earmarked for roads and public transit."

"The cities that are responsible for raising their own revenue tend to be more efficient and accountable than those that live off transfers from other levels of government," Kitchen said.

"Road pricing" is being used around the world, from the United States to Sweden and Singapore.

Queen's Park has rejected the idea here for now, though many experts believe resistance to the idea is dropping and experience in other countries shows the public can be sold on the benefits if tolls are rolled out carefully.

Conference organizer Marty Collier, of Healthy Transport Consulting, says an Ontario discussion on road pricing is long overdue.

It needs to happen now, he said, so that people will be familiar with the subject when, in 2013, existing funding runs out and Metrolinx needs to reopen the issue of how to pay for more transit, walking and cycling amenities.

"We're just trying to have a rational discussion about road pricing and can it be used, not just to pay for infrastructure, but also as a way to give people incentives to go with other modes.

"I think people want to see what's happened around the world, learn from other people's successes, other people's failures, and see if it can be applied at some point," he said.

There's more to getting people to take transit than just adding buses or trains in service.

For those who choose to continue driving, he said, "Maybe it's time for people to pay for whatever they actually use."