RWY TRANSGRESS DURING TAXI OUT.

Narrative

WE WERE CLRED TO TAXI FROM THE GATE TO RWY 29. I HAD TO START THE #1 ENG WHICH THE CAPT DELEGATED TO ME TO START; PERFORM THE TAXI CHKLIST; AND BEGIN TO PREPARE FOR THE TKOF CHKLIST ALL IN A RELATIVELY SHORT PERIOD. AFTER I STARTED THE #1 ENG (MY HEAD WAS DEEP IN THE COCKPIT WATCHING THE ITT AND COVERING THE CONDITION LEVER AND ECU BUTTON WITH MY HANDS) I LOOKED UP AND REALIZED WE HAD JUST CROSSED RWY 29 WITHOUT A CLRNC TO DO SO. I ASKED THE CAPT AND HE CONFIRMED WE HAD JUST CROSSED RWY 29. I TOLD HIM CLRNC TO TAXI MEANT; COULD CROSS ALL RWY EXCEPT THE RWY CLRED TO. THE CAPT I BELIEVE WAS USED TO OP AT MUCH LARGER ARPTS WHERE A 'CLRED TO TAXI TO RWY' WOULD NOT CROSS THAT RWY. HE SEEMED UNFAMILIAR WITH THE TAXI CLRNC DEFINITION. I BELIEVE AT ARPTS WHERE TXWYS CROSS THE ACTIVE RWY WHEN TAXIING TO THE ACTIVE RWY; AN ADDITIONAL REMINDER SHOULD BE INCLUDED SUCH AS HOLD SHORT OF RWY; TO ENHANCE SAFETY. PERHAPS I SHOULD HAVE WAITED UNTIL WE WERE ON THE OTHER SIDE OF THE RWY TO START THE ENG. TO MY KNOWLEDGE THERE WERE NO OTHER ACFT OPERATING AT WORCESTER ARPT AREA AT THAT TIME.