Air Traffic Control Time Certified In Pos 1 (yrs) 7.5
Distraction
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Human Factors; Procedure
While working LC-3; I started crossing after an aircraft departed. I crossed one at S; N5; and T. I then crossed 2 at P. I scanned the runway and observed aircraft clear at all intersections but failed to notice the 2nd aircraft at P had not yet entered the runway. Aircraft Y was about 1000 feet down RWY 27R when Aircraft X called me and said he had not yet crossed the RWY when I cleared Aircraft Y for takeoff. I evaluated his position; which did not appear to be past the hold lines and Aircraft Y was already passing through 60 kts according to the ASDE. I told Aircraft X to hold position and allowed Aircraft Y to continue departure roll. Once airborne I crossed Aircraft X first and then proceeded to cross all remaining aircraft at the other intersections. I can't recall how I messed this up. I don't know if Aircraft X was slow to taxi or how I didn't account for the second aircraft at P.Always use procedures and patterns. I should have only crossed one at P to be consistent with the other intersections. I should be more aware of aircraft that taxi very slowly to make sure they don't get lost in the pack.
ATL Tower Controller reported of crossing two aircraft and then doing other duties. Controller then cleared an aircraft for takeoff; second crossing traffic advised Controller they have not crossed yet. Controller had crossing aircraft hold short of runway allowing departing aircraft to get airborne. Controller thought the second crossing aircraft was slow in its taxi and that is why they forgot about it.