This featured a `` rapid transit subway '' operated with subway trains , to be located off-street beside Yonge Street , partly in open cut , from Eglinton Avenue as far as College Street , then continuing directly under Yonge and Front Streets to Union Station .
The first part of the subway , replaced a very busy streetcar route , and followed Yonge Street from Eglinton Avenue south to Front Street , then turned west for one block to end at Bay Street , next to the city 's main railway station Union Station and so the subway station was also called Union .