UNAUTH RWY XING BY SUPPLEMENTAL CARRIER.

Narrative

UPON LEAVING THE RAMP (WHICH IS S OF RWY 28) MY FO CALLED FOR TAXI INSTRUCTIONS. THE CTLR RESPONDED 'TAXI RWY 28; HOLD SHORT OF 32.' LTT Z WAS ALSO TAXIING OUTBOUND AND WAS #1. HE WAS CLRED TO CROSS RWY 28 TO HIS RAMP. (WE WERE CLRED SIMULTANEOUSLY). I HAD ONLY BEEN TO THIS ARPT 4-5 TIMES AND WHEN USING RWY 28 WAS ALWAYS GIVEN INSTRUCTIONS TO CROSS THE RWY AND TAXI ON THE N PARALLEL. BASED ON THIS EXPERIENCE I THOUGHT THE CTLR WANTED ME TO FOLLOW ACFT Z ACROSS THE RWY AND TAXI TO RWY 28 FROM THERE. RWY 28 WAS THE ACTIVE AND AN MLG ACR WAS IN POS 6000 FT TO THE E. APPARENTLY ACR Y HAD BEEN ISSUED A TKOF CLRNC WHICH HAD TO BE CANCELLED AS THE CTLR WANTED ME TO USE THE S PARALLEL. (THOUGH THIS WAS NEVER STATED). ALTHOUGH I SHOULD HAVE VERIFIED A VAGUE TAXI INSTRUCTION; AND IN HINDSIGHT I CANNOT BELIEVE I DID NOT; I FELL INTO A TRAP OF REPETITION AND FEELING I KNEW WHAT THE CTLR WANTED; HE WAS JUST BUSY AND FORGOT TO BE MORE SPECIFIC. I FEEL 2 FACTORS CONTRIBUTE TO THIS ERROR IN JUDGEMENT. THE FIRST; FATIGUE. I HAD BEEN ON DUTY 10 HRS. THOUGH THIS IS NOT A LONG TIME UNDER NORMAL CIRCUMSTANCES; I HAD BEEN OFF FOR 2 1/2 DAYS. THOUGH I TRY TO FIGHT IT WHEN I AM OFF I 'AUTOMATICALLY' RETURN TO A NORMAL SCHEDULE -- UP IN THE DAYTIME AND SLEEPING AT NIGHT. THIS PROBLEM IS SOMEWHAT ENDEMIC TO THE FREIGHT INDUSTRY. SPECIFICALLY; I HAD ABOUT 2 HRS SLEEP (A NAP FROM 0100-0300) IN THE PREVIOUS 24 HRS. THOUGH THIS IN ITSELF IS NO EXCUSE FOR POOR JUDGEMENT I AM CERTAIN THAT FATIGUE DID; INDEED; PLAY SOME ROLE IN THIS INCIDENT. THE SECOND FACTOR; I BELIEVE; WAS A VAGUE TAXI CLRNC. GIVEN THE NORMAL FLOW OF GND TFC AND THE ISSUANCE OF CLRNC TO ACFT Z TO CROSS RWY 28 IMMEDIATELY PRIOR TO MY CLRNC I AM CERTAIN HAD THE CTLR GIVEN SPECIFIC INSTRUCTIONS AS TO WHAT HIS INTENTIONS WERE NO INCIDENT WOULD HAVE OCCURRED. AS A BRIEF ASIDE; RETURNING TO SYR THAT EVENING THE CTLR WORKING GND WAS VERY PRECISE WITH HIS INSTRUCTIONS. WHETHER DUE TO THE EVENTS DESCRIBED OR JUST NORMAL WORK HABITS I DON'T KNOW; BUT I SURE WOULD HAVE APPRECIATED WORKING WITH HIM THE MORNING. FINALLY; AS PREVIOUSLY STATED I FELL INTO A TRAP THAT MORNING. I THOUGHT I KNEW WHAT THE CTLR WANTED ME TO DO; AND RATHER THAN INCONVENIENCE HIM AT A BUSY HOUR I PROCEEDED WITH WHAT I ASSUMED WERE HIS INTENTIONS. BELIEVE ME I WILL NEVER EXECUTE ANY PROC IN THE FUTURE WITHOUT MAKING 100 PERCENT CERTAIN ALL THOSE INVOLVED CLRLY HAVE THE SAME INTENTIONS IN MIND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR GAVE RUNDOWN ON WORK SCHEDULING AND WORK/REST CYCLE. SAYS FATIGUE WAS DEFINITE FACTOR. TAXIWAY 'H' IS NARROW AND ATC SOMETIMES WANTS THEM TO USE 'G' AND 'A' TO GET TO RWY 28. ACFT Z WAS NOT GOING OUT FOR DEP; BUT WAS RELOCATING ON THE ARPT. RPTR HAS RECEIVED LETTER FROM FAA SAYING THAT THE INCIDENT WAS UNDER INVESTIGATION.