Narrative:

After clearing bos runway 4R with instructions to hold short of runway 4L and change to the parallel tower frequency, we proceeded up very close to runway 4L and came to a full stop. The captain anticipated a rapid crossing of runway 4L after a commuter airliner departure. He was ready to expedite across runway 4L to assist with rapid traffic flow. The captain apparently mistook a tower command to another aircraft for our call sign. I heard only the words 'cleared' and '4L' because the controled spoke too fast and my occupation with equipment reset. Before I could confirm that we were cleared to cross, the captain had added power and moved us onto runway 4L (our nose was right on the edge of the runway). The radio was extremely busy with other tower xmissions. I took no action to stop the captain because it seemed logical at that instant that we should be cleared to cross and I was in error for not hearing our call sign. The first commuter had just departed and the captain was visually clearing the entire runway and final approach. The events occurred so rapidly that by the time I could get out a transmission we were on the active runway that had another aircraft cleared for takeoff. Once we realized what had transpired, it was better to continue across rather than stop on the active runway 4L. We were off the other side before the aircraft flew overhead. This crew operated together for an entire months flight schedule. We have a good, professional working relationship and have strictly followed company procedures. Backing each other up in cases of discrepancies came naturally and promptly.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR AFTER LNDG TAXIS ACROSS ACTIVE RWY WITHOUT CLRNC.

Narrative: AFTER CLRING BOS RWY 4R WITH INSTRUCTIONS TO HOLD SHORT OF RWY 4L AND CHANGE TO THE PARALLEL TWR FREQ, WE PROCEEDED UP VERY CLOSE TO RWY 4L AND CAME TO A FULL STOP. THE CAPT ANTICIPATED A RAPID XING OF RWY 4L AFTER A COMMUTER AIRLINER DEP. HE WAS READY TO EXPEDITE ACROSS RWY 4L TO ASSIST WITH RAPID TFC FLOW. THE CAPT APPARENTLY MISTOOK A TWR COMMAND TO ANOTHER ACFT FOR OUR CALL SIGN. I HEARD ONLY THE WORDS 'CLRED' AND '4L' BECAUSE THE CTLED SPOKE TOO FAST AND MY OCCUPATION WITH EQUIP RESET. BEFORE I COULD CONFIRM THAT WE WERE CLRED TO CROSS, THE CAPT HAD ADDED PWR AND MOVED US ONTO RWY 4L (OUR NOSE WAS R ON THE EDGE OF THE RWY). THE RADIO WAS EXTREMELY BUSY WITH OTHER TWR XMISSIONS. I TOOK NO ACTION TO STOP THE CAPT BECAUSE IT SEEMED LOGICAL AT THAT INSTANT THAT WE SHOULD BE CLRED TO CROSS AND I WAS IN ERROR FOR NOT HEARING OUR CALL SIGN. THE FIRST COMMUTER HAD JUST DEPARTED AND THE CAPT WAS VISUALLY CLRING THE ENTIRE RWY AND FINAL APCH. THE EVENTS OCCURRED SO RAPIDLY THAT BY THE TIME I COULD GET OUT A XMISSION WE WERE ON THE ACTIVE RWY THAT HAD ANOTHER ACFT CLRED FOR TKOF. ONCE WE REALIZED WHAT HAD TRANSPIRED, IT WAS BETTER TO CONTINUE ACROSS RATHER THAN STOP ON THE ACTIVE RWY 4L. WE WERE OFF THE OTHER SIDE BEFORE THE ACFT FLEW OVERHEAD. THIS CREW OPERATED TOGETHER FOR AN ENTIRE MONTHS FLT SCHEDULE. WE HAVE A GOOD, PROFESSIONAL WORKING RELATIONSHIP AND HAVE STRICTLY FOLLOWED COMPANY PROCS. BACKING EACH OTHER UP IN CASES OF DISCREPANCIES CAME NATURALLY AND PROMPTLY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.