On weekdays the first northbound Red Line train (to the University Medical Center Station) leaves the 900 East & 400 South Station at about 5:15 am and the first southbound train (to the Daybreak Parkway Station) leaves at about 5:30 am.
On Saturdays the first northbound train leaves at about 6:45 am and the first southbound train leaves at about 7:00 am.