FLC DEV FROM CLRNC IN UNAUTHORIZED UNCOORD RWY ENTRY DURING CONFUSION IN TAXIWAY MARKING PLACEMENT VISIBILITY GUIDANCE.

Narrative

ON THE LNDG ROLLOUT ON RWY 4R AFTER THE ILS 4R APCH AT BOSTON LOGAN; WE WERE INSTRUCTED TO TURN L AT YANKEE TAXIWAY BY THE LCL CTLR. THIS INSTRUCTION WAS GIVEN WHILE THE THRUST REVERSERS WERE DEPLOYED WITH THE ASSOCIATED NOISE PRESENT. TO CONFIRM THE INSTRUCTION; I ASKED THE COPLT (PNF) 'LEFT AT YANKEE?' TO WHICH HE REPLIED; 'NEXT L' AS THE CTLR WAS ADDING TO HIS PREVIOUS INSTRUCTION; 'IT'S THE EASY L TURN'. AT THIS TIME; WE WERE PASSING THROUGH THE AREA ON RWY 4R WHERE THERE IS A CONFLUENCE OF TAXIWAYS AND RWY 15R/33L. I SAW A MARKER RWY 15R INSTEAD OF YANKEE TAXIWAY. I IMMEDIATELY REALIZED MY MISTAKE AT THE SAME TIME THE LCL CTLR SAID 'NO; NOT THERE; MAKE AN IMMEDIATE 180'. THE IMMEDIATE 180 DEG TURN PLACED THE ACFT'S NOSE ENCROACHING ON RWY 4R WHICH WE HAD BARELY LEFT. THE FO NOW DECIDED TO ASSERT HIMSELF AND FIRMLY ADVANCED THE THROTTLES JUST AS THE LCL CTLR WAS INSTRUCTING US NOT TO ENTER THE RWY. AS WE WERE NOW ALREADY ON THE RWY; I ADVANCED THE THROTTLES FURTHER AND SWEPT ON TO YANKEE TAXIWAY WHERE WE AGAIN EXITED THE RWY. WHEN THE CTLR HAD SEEN THAT WE WERE ALREADY BACK ON RWY 4R AFTER THE 180 DEG TURN; HE CANCELLED THE LNDG CLRNC OF THE ACFT ON THE APCH BEHIND US. HE IMMEDIATELY RESCINDED THE CANCELLATION; HOWEVER; AND AGAIN CLRED THE ACFT TO LAND AFTER OUR FAST TAXI AND EXIT AT YANKEE. THE MAJOR CONTRIBUTING FACTORS IN THIS INCIDENT WERE MISCOM; A BREAKDOWN IN CREW COORD; AND CONFUSION OF TAXIWAY MARKINGS. THE FO'S 'NEXT LEFT' COMMENT WAS MEANT TO CONVEY 'NEXT TAXIWAY' AND THE CTLR'S INTENT WITH HIS 180 DEG TURN WAS MISINTERP TO MEAN TO CONTINUE TO YANKEE TAXIWAY BECAUSE IT WAS NOT; TO MY KNOWLEDGE; FOLLOWED BY A 'AND HOLD SHORT OF THE RWY' IN THE SAME INSTRUCTION. I THINK THE QUICKNESS OF OUR 180 DEG TURN TOOK HIM BY SURPRISE AND HE WAS VERY BUSY AT THE TIME. FURTHERMORE; TAXIWAY MARKINGS ARE OFTEN CONFUSING DUE TO NONSTANDARD PLACEMENT IN RELATION TO THE TAXIWAY BEING LABELED AT DIFFERENT ARPTS. SOME MARKINGS ARE PLACED PRIOR THEIR TAXIWAY WHILE SOME ARE FOUND ON THE OTHER SIDE; PAST THE SUBJECT TAXIWAY. THE ENSUING CONFUSION LED TO A BREAKDOWN IN CREW COORD AND LED US TO COMPOUND MY ORIGINAL ERROR.