The long-awaited second platform is set to open at Union Station on Monday.

Previously there was one platform in the centre of the station, allowing riders to access both the Yonge and University subway lines. The single platform was often overcrowded after sporting events like Maple Leaf, Raptor and Blue Jay games, and during the tourist season.

Union Station during its construction phase. The second platform opens on Monday, August 18. (TTC)

Transit riders will now use one platform to board Finch-bound trains on the Yonge Street line and the other to head to destinations on Downsview-bound trains on the University line. There will be two stairwells leading to the different platforms.

With the completion of construction, Union Station is transformed from a centre platform configuration to a side platform configuration. The rehabilitated centre platform is now for Downsview-bound trains and the new platform will be for Finch-bound trains.

The TTC says the addition of the second platform will double the passenger capacity at the station.

The new platform will feature new ceramic wall tiles at track-level and new glazed glass partitions along the ramped walkways. (TTC)

The new design also provides a connection to the PATH, the underground concourse in downtown Toronto.

According to the TTC, the total cost of the second platform and other concourse improvements is $137.5 million. The project is being funded by the federal, provincial and Toronto governments.

In preparation for the opening, there will be no service between Union and St Andrew stations this weekend. Wheel-Trans service will be available for customers requiring an accessible connection.