Toronto's growing population will put increasing demands on the subway system in the near future, which TTC CEO Andy Byford says necessitates a closer look at prioritizing the building of a downtown relief line.

The TTC is putting forward a discussion paper, at a meeting on Wednesday that suggests Toronto should prioritize building a relief line to reduce the pressure on the existing Yonge Street subway line.

While Byford says the TTC is taking steps to move as many people as they can on the subways in the existing system, it is coming to a point where there will be no more wiggle room.

"We’re just holding back the tide, we really do need to start thinking about a relief for that line, so to provide additional capacity to get people from the suburbs downtown," Byford told CBC Radio's Metro Morning.

"The way to do that is to get people off the Bloor-Danforth line earlier, so that they don’t interchange onto the Yonge line."

While some may argue that a so-called downtown relief line will bring the most benefit to downtown residents, Byford said it will actually help the people living outside the core make their way into the city more efficiently.

"At the end of the day, this isn’t a private shuttle for people living around Queen and King," he said.

"This is a line to get people from the suburbs, primarily, into the prime traffic objective — in other words, where people want to go — which is the commercial and financial centre of downtown Toronto."

There is no plan for funding a downtown relief line at the moment, which Byford said underscores the need to start the discussion.

"Let’s get that debate going, obviously funding is an issue, but let’s at least start the talking," he said.