CAPT OF AN MD80 INADVERTENTLY CROSSED THE ACTIVE RWY WITHOUT CLRNC DUE TO BEING DISTR FROM FOLLOWING THE NORMAL TAXI RTE.

Narrative

I TAXIED ACROSS AN ACTIVE RWY WITHOUT CLRNC. I THOUGHT IT WAS AN INACTIVE RWY. I DID CLR VISUALLY FOR TFC ON THE RWY; BUT DID NOT HAVE CLRNC TO CROSS. FORTUNATELY; THERE WAS NO CONFLICT WITH ANY ACFT TAKING OFF OR LNDG. SEVERAL FACTORS LED UP TO THIS EVENT. I HAVE BEEN A PROFESSIONAL PLT FOR 32 YRS AND THIS IS THE WORST MISTAKE I HAVE EVER MADE. I AM A LINE INSTRUCTOR FOR MY AIRLINE AND HAVE BEEN FOR SEVERAL YRS. THIS WAS A TRAINING FLT AND MY STUDENT WAS AN FE UPGRADING TO FO. I WAS TAXIING SINGLE ENG TO CONSERVE FUEL. I TOLD THE STUDENT TO START THE REMAINING ENG. HE INFORMED ME IT WOULD NOT START. AT THIS POINT I DIVERTED MY ATTN FROM TAXIING TO SEE WHAT THE PROB WAS. HE HAD NOT TURNED ON THE IGNITION. I CORRECTED THE START SEQUENCE AT THIS TIME AND DID NOT MAKE MY TURN ONTO THE PARALLEL TXWY. I MISTAKENLY THOUGHT THE RWY IN FRONT OF ME WAS THE INACTIVE E/W RWY. MY FO AT THIS POINT REMARKED 'WE'RE FINE AND CLRED ALL THE WAY.' AFTER XING THE RWY; I REALIZED MY MISTAKE. GND CTL SAID NO CONFLICT OCCURRED AND RECLRED US TO THE ACTIVE. I WAS MORTIFIED AND SICK ABOUT THIS GROSS ERROR. CONTRIBUTING FACTORS: I BROKE MY PERSONAL POLICY OF SINGLE ENG TAXI WITH A STUDENT AT AN UNFAMILIAR ARPT. I LET FUEL CONSERVATION OVERRIDE MY SAFETY BUFFER. I SHOULD HAVE STARTED BOTH ENGS AT THE GATE PRIOR TO TAXI. THE TAXI RTE FROM THE TERMINAL TO RWY 35R IS SOMEWHAT CONFUSING WITH MULTIPLE TURNS AND TXWY LETTERING AND LIGHTING. HUMAN PERFORMANCE CONSIDERATIONS: RECENT BREAK UP OF LONG TERM RELATIONSHIP. LOSS OF CONCENTRATION DUE TO PREOCCUPATION WITH MAJOR SURGERY SCHEDULED FOR NEXT MONTH.