When it comes to Premier Doug Ford’s proposal to build a 55-kilometre tunnel to lessen congestion on Highway 401, the devil will be in the details.

Ford presented his plan to build a tunnel from Mississauga to Scarborough as a bold vision to help deal with traffic that infuriates millions of drivers across the Toronto region.

But it could also be a project that could cost taxpayers dearly and take decades to build.

When Ford first laid out his case for building the tunnel, he hit the right notes. Ford promised to conduct a feasibility study to determine if the project makes sense for Ontario financially.

But then Ford made a dangerous turn.

After promising to conduct a feasibility report, which would protect taxpayers from a potential financial boondoggle, Ford declared: “I’ll tell you one thing, we’re getting this tunnel built.”

So, which is it?

Is Ford going to be a prudent manager of taxpayer dollars and conduct a thorough study and consider its recommendations, or is he pushing forward with this project without even knowing the price tag or timetable?

The premier owes taxpayers answers.

Maybe this is going to be one of the best infrastructure projects in the history of infrastructure projects. Or maybe it will cost tens of billions of dollars, take decades to build, and cause even worse traffic gridlock until it’s completed.

The point is, we don’t know. And the premier shouldn’t decide until we do.

Ontario taxpayers have reason to be worried. The province doesn’t have a great track record delivering big infrastructure projects on budget in a timely manner.

The Eglinton Crosstown LRT in Toronto was supposed to open in 2020. The project is at least $1 billion over budget, years behind schedule, and has been plagued with at least 260 quality control issues.

The Crown corporation in charge of building the LRT couldn’t even lay down the track right: tracks were off by a few millimeters and construction workers had to rip much of it up.  

Then there’s Ford’s signature Ontario Line, a relief subway line for downtown Toronto. It’s already $16 billion over budget and still years away from completion.

How can Ontario taxpayers have faith in the government to build the largest tunnel in the world with this kind of a track record?

Then there’s the potential cost of the tunnel itself.

The most comparable project is the Big Dig in Boston, a recently completed tunnel that is eight lanes wide. The cost to build that 2.5-kilometre tunnel was $8 billion.

For context, Ford wants to build one that’s 22 times longer. Even if Ford found a way to build his tunnel at half the cost, we’d still be looking at an $88-billion price tag.

That money could otherwise pay for 35 new state-of-the-art hospitals, is more than double this year’s education budget, and could cover every Ontarian’s provincial income tax bill for 18 months.

Ontario has the most sub-national debt in the world, at more than $400 billion. Ford’s overspending put Ontarians on the hook for $14 billion in debt interest payments this year. And the Ford government is running a deficit of nearly $10 billion.

This province is not in the financial shape to undertake the most expensive infrastructure project in Canadian history without a plan.

The bottom line is we don’t know if this is a good idea or not. The devil is in the details. It might be a stroke of genius, or it might be foolhardy.

If Ford wants taxpayers to take his proposal seriously, he owes it to Ontarians to conduct the feasibility report and make it fully available to the public before any major decisions are made.

After all, there’s tens of billions of dollars of taxpayer money at stake.