Without a $3.2 billion downtown subway relief line commuters will face nightmarish overcrowding in the coming years, a new report reveals.

The study, by TTC and City of Toronto staff, concludes that the Yonge subway line and a number of GO rail corridors are already overcrowded but current projects to address surging ridership, like an extension of the Yonge subway line to Richmond Hill, won’t suffice in the long run.

By 2031, transit ridership into the downtown is expected to grow by 51 per cent, and the population south of College Street from Bathurst to Parliament will surge by 83 per cent, the report states.

The number of morning peak-period trips into downtown will also jump from 155,000 to 236,000.

Making matters worse, a proposed extension of the Yonge subway line from Finch Avenue to Highway 7 “is forecast to result in ridership exceeding the capacity of the Yonge subway line before 2031 if no further action is taken to relieve overcrowding on the line.”

Larger Toronto Rocket trains and streetcars, and an Automatic Train Control system will increase line capacity and offer some relief to the overburdened system, but not nearly enough, the report states.

“The most-serious capacity issues are related to long- and medium-distance trips from the east and north.”

“The construction of an initial phase of a “Downtown Relief Line” on the east side of the downtown would address these capacity concerns for the foreseeable future.”

“This relief could be provided by a…subway line from Pape Station into the downtown.”

It would connect at St. Andrew station.

The report will presented at a TTC board meeting on Wednesday.

Read the full report here.