A321
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors
PHL on 9/35 configuration; new mitigated headings went into effect. Workload is very high on this configuration. It is the busiest position in the Tower under these circumstances. I was working Local East with traffic departing 9L and landing intersecting Runway 35. Traffic on short final to Runway 35 and an A321 in position on 9L; I crossed two aircraft at Taxiway November; an E170 first then an A321 and one aircraft at Taxiway 'E'. Landing traffic cleared the departure runway and I looked to see if my crossings were complete. I saw the first aircraft clearing the runway at November and though it was my second. I cleared the A321 for take off and immediately realized my error as the E170 was still moving. I immediately canceled the take off clearance. The aircraft had not appeared to move; but when the pilot was questioned; he said he moved about ten feet. The ASDE-X did not alarm; nor did the 'bars' go up. Don't have a complex operation during a procedure change. Taking the Runway 35 arrivals out of the equation would have dramatically reduced the workload. New mitigated headings were taking attention away from other tasks. Having clearance or Ground Control write the heading on the departure strip would have been a big help.
PHL Controller cleared a second aircraft for take off failing to note crossing traffic down field; the reporter issuing alternate instructions to secure separation.