GND COLLISION AVERTED BY ALERT ATCT GND CTLR'S WARNING TO TAXIING TFC. UNAUTH RWY ENTRY.

Narrative

WE WERE OPERATING AS AN EXPRESS CARRIER IN SANTA BARBARA. FLT LEFT THE GATE AT XA05 LCL TIME OUR CLRNC WAS TO TAXI TO RWY 7 AND HOLD SHORT OF RWY 15R. MY FO ACKNOWLEDGED THE CLRNC. AS WE BEGAN OUR TAXI WE STARTED TO DO OUR TAXI CHKLIST. AS WE APCHED RWY 15R ON TXWY ALPHA I REALIZED I HAD FORGOTTEN THE HOLD SHORT CLRNC. AT THAT TIME THE TWR WAS CONCEIVED WITH OUR ABILITY TO HOLD SHORT. AND AS I WAS SLAMMING ON THE BRAKES THE TWR AGAIN TOLD US TO HOLD SHORT. WHEN WE STOPPED; OUR ACFT WAS AS CLOSE TO THE RWY AS YOU COULD GET WITHOUT XING IT. AS WE LOOKED TO THE LIGHT WE SAW A LIGHT ACFT ROLLING TO A STOP. THE TWR THEN TOLD THE CESSNA TO EXIT THE RWY AT TXWY ALPHA ON THE OTHER SIDE OF THE RWY. WE WERE THEN TOLD TO CROSS RWY 15R AND TO CONTINUE OUR TAXI TO RWY 7. AT THE END OF THE TXWY WE WERE GIVEN A NUMBER TO CALL WHEN WE ARRIVED IN LOS ANGELES. CONTRIBUTING FACTORS WERE MY PREOCCUPATION WITH MAKING A FLOW TIME TO LOS ANGELES; AND RWY CONSTRUCTION GOING ON AT RWY 15L. THERE WERE CONES AND BARRICADES UP ALONG THE TXWY AND I REMEMBER THINKING TO MYSELF SECONDS BEFORE THIS HAPPENED THAT THERE WASN'T A LOT OF ROOM ON THE TXWY TO TAXI. THINGS I'VE LEARNED ARE THAT I NEED TO PAY MORE ATTN TO EVERYTHING GOING ON INSIDE AND OUTSIDE OF THE COCKPIT. I HOPE THIS RPT HELPS SOMEBODY ELSE.