sentences:  The Toronto Transit Commission contains a mix of one-person train operation and two-person operation.Since its opening in 1985, the light-metro Scarborough RT line is operated with a single operator, while the heavy-rail Yonge-University-Spadina and Bloor-Danforth lines have always operated with two-person crews of a train operator and guard (conductor).The guard is responsible for operating the doors, as well as observing the platform.