T1 Line Speed: 1.544Mbps each way?

The rated speed of a T1 line purchased from the phone company is 1.544 Mbps. Is that the speed in each direction — i.e., theoretically 1.544 Tx max. and 1.544 Rx max.? Or is it 1.544 Mbps total — that is to say, Tx speed + Rx speed = 1.544 max. ?