Medium Large Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4.5
Distraction; Confusion; Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Procedure; Human Factors
I was working Local East during a busy departure session.  I cleared an aircraft for takeoff and ground asked me for a crossing behind my departure at taxiway Tango.  I approved it and did my own crossings at taxiway N and E.  When my crossings were complete I scanned the runway and cleared Aircraft X for takeoff.  Aircraft Y had not yet entered the runway at T.  Aircraft X didn't roll right away and then asked about the traffic crossing at T.  Traffic was busy and I was trying to get one more departure out in front of my next 35 arrival.  I forgot about the crossing I gave to ground at Tango.  I did have the departure strip flipped over so I wouldn't clear my departure for takeoff but when my traffic was done crossing at E & N; I flipped it back over and rolled my departure.  I scanned the runway before I cleared him but Aircraft Y was not yet on the runway.  It's simply my fault for forgetting.
A PHL Tower Controller reports of having a runway incursion because he forgot about traffic crossing and cleared an aircraft for takeoff.