AN ACR X LNDG RWY 18L IS SWITCHED TO GND AND CLRED ACROSS RWY 18C AS ACR Y IS CLRED FOR TAKEOFF ON RWY 18C. THE SIT IS RECOGNIZED AND ACR Y'S TAKEOFF IS ABORTED WHILE ACR X IS EXPEDITED.

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WHILE WORKING GND CTL IN MEMPHIS TWR DURING A BUSY MORNING OUTBOUND PUSH; I HAD BEEN RELEASED CTL OF RWY 18C FOR CROSSING TO SEND ACFT TO RWY 18L TO ACCOMMODATE SIMULTANEOUS DEPS. DURING THIS PERIOD AN A320 (Y) REQUESTED RWY 18C BECAUSE OF WEIGHT. UNDER NORMAL CONDITIONS HE WOULD HAVE BEEN GIVEN RWY 18R. AT THE TIME HE WAS NEARING READY FOR TAKEOFF I STARTED GETTING ALL THE OUTBOUND TFC CLR OF RWY 18C AND GAVE THE RWY BACK TO LOCAL. AT THAT TIME LOCAL HAD CLRED ACR X AN EMBRAER 145 TO LAND ON RWY 18L; HE TURNED OFF AND WAS TOLD TO CONTACT GND. I THEN CROSSED ACR X ON RWY 18C AT THE SAME TIME ACR Y WAS CLEARED FOR TAKEOFF. THE LOCAL CTLR ABORTED ACR Y'S TAKE OFF AND I EXPEDITED ACR X ACROSS RWY 18C. THE ACFT WE NEVER CLOSER THAN 6000 FT AT TAXI SPEED. UNDER NORMAL PROCEDURES LOCAL WOULD HAVE TURNED ACR X OFF RWY 18L AND HELD SHORT OF RWY 18C ON TWR FREQ OR CROSSED RWY 18C THEN CONTACTED GND. AT THE TIME I HAD 13 ACFT ON MY FREQ. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR INDICATED THAT HEAVY WORKLOAD WAS AN ISSUE -- HE WAS WORKING 13 ACFT AT THE TIME OF THE RWY INCURSION EVENT AND SIMPLY MISSED THE POTENTIAL CONFLICT. HE INDICATED THAT LOCAL SWITCHED ACR X TO GND UPON CLRING RWY 18L; AND BECAUSE OF THE VERY SHORT DISTANCE BETWEEN RWY S 18L AND 18C; THERE IS A SIGNIFICANT OPPORTUNITY FOR THIS SORT OF 'TRAP' TO DEVELOP. HE SUGGESTS THAT ACFT SHOULD REMAIN WITH TWR IF RWY 18C IS ACTIVE.