The Ontario government will contribute more than $150 million for planning and design work on Toronto's so-called downtown relief subway line.

It's unclear exactly how the provincial funding will be spent, with Ontario Transportation Minister Steven Del Duca, telling reporters "it was too early" to provide an itemized list. Instead, Del Duca said provincial and city staff will meet in the coming weeks to set planning goals.

Neither the provincial nor municipal politicians indicated the funding would mean Toronto would see the relief line built more quickly than the anticipated more than 10-year timeline.

Transit experts in Toronto have talked about the need for a downtown relief subway line for decades as a way to alleviate crowding on the Yonge-University-Spadina Line.

Relief line

It's usually drawn on the map as a U-shaped line that proceeds south from the Bloor-Danforth line in the east, cuts through the downtown core, then turns north again to reconnect with the west side of the Bloor-Danforth line. But where the line should start and end, and where it should go through the core, has always been open to debate.

TTC chairman and Coun. Josh Colle said he believed some of the funds would go toward planning where stops should go — and to study any geotechnical challenges that would come from burrowing underneath a city of 2.8 million people.

That will help the city to define both the project's cost and its timeline, after which they can then look to the other levels of government for help, Colle said.

"The numbers that have always been used have kind of been 10-12 years, but you don't know until you've done the detailed design what you're actually building."

'Critical projects'

Toronto Mayor John Tory said the city "took years off" when it did not expand its transit infrastructure, which has led to the current problems of overcrowding.

"The fact is the Yonge Street subway is over capacity, which is why both SmartTrack and the subway relief line are both critical projects for our city," Tory said. "Toronto, in particular needs more transit. We need it sooner more than later."

Tory said the relief line will work with SmartTrack, the proposed rail line to connect the downtown core with parts of the GTA, to ease the pressure on the Bloor-Danforth and Yonge Street subway lines.

The fallible nature of the system showed itself again Wednesday as a smoking subway cable shut down the Bloor-Danforth line for three hours during the height of the morning commute.

Passengers on the overcrowded Yonge-University-Spadina Line may see several trains pass during peak times before they can board. (Tariq Fancy/Twitter)

The advent of the so-called relief line would ease not only the pressure on an overcrowded system, but also give transit operators an alternate route by which they could divert passengers underground, the TTC's chief executive officer Andy Byford said.

"In normal circumstances it does provide relief to that pinch point at Yonge and Bloor," Byford told reporters Wednesday afternoon. "But it's not just a relief line, it's an alternative line and goodness knows we could have done with that this morning when we had all those problems.

"Now, if you have Line 1 or Line 2 go down, pretty much you only have one option — shuttle buses."

Tory said that expects some of the $840 million the federal government earmarked for the TTC last month will go toward these types of infrastructure improvements.

That money is to come from the $3.4 billion set aside for transit in March's federal budget.