Narrative:

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 north and east. 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 east & north; 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.

Google
 

Original NASA ASRS Text

Title: A PHL Tower Controller reports of having a runway incursion because he forgot about traffic crossing and cleared an aircraft for takeoff.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.