ACR LGT ACFT WAS TAXIED WHEN EXCEEDING THE GROSS APPROVED TAXI WT LIMITATION.

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WE WERE CLOSE TO PUSHBACK TIME WITH A FULL AIRPLANE. JUST PRIOR TO PULLING THE JETWAY; THE GATE AGENT ARRIVED TO PULL 2 PAXS OFF OF THE FLT FOR WT REASONS. THE AGENT CLOSED THE DOOR. WE STARTED ENGS AND PWRED BACK FROM THE GATE; THEN TAXIED TO THE ACTIVE RWY. WE HAD NOT RECEIVED WT DATA VIA ACARS AS WE APCHED THE HOLD SHORT; SO WE ASKED GND IF WE COULD PULL INTO THE RUNUP PAD TO AWAIT NUMBERS. WE DID NOT RECEIVE OUR WT DATA PROMPTLY SO WE CONTACTED LOAD CTL OVER THE RADIO. THEY WERE UNSURE WHAT THE HOLDUP WAS SO WE CONTACTED DISPATCH. DISPATCH INFORMED US THAT THEY WERE WAITING FOR THE FINAL NUMBERS FROM THE WT AND BAL DEPT. WE CONTINUED TO WAIT; AND WHEN THE DELAY STARTED TO BECOME EXCESSIVE WE AGAIN CONTACTED DISPATCH FOR AN UPDATE. BY THIS TIME WE WERE BELOW TKOF GROSS WT; BUT DISPATCH INFORMED US THAT WE HAD TAXIED OUT OF THE GATE ABOVE GROSS TAXI WT. WE WERE TOLD TO RETURN TO THE GATE FOR APPROPRIATE ACTION. LEAVING THE GATE WITHOUT WT DATA IS AN APPROVED PROC AND IS THE NORM AT OUR CARRIER; AS IT IS AT MOST AIRLINES. BUT IN THOSE FEW INSTANCES WHEN IT COMES RIGHT DOWN TO THE WIRE; THE ACFT SHOULD BE HELD AT THE GATE UNTIL THE WT DATA IS COMPLETED. THE PRESSURE TO GET AN ON-TIME DEP MAY OCCASIONALLY PRECLUDE DISPATCH OR LOAD CTL FROM DELAYING A FLT IN THESE CLOSE CASES. THE DIFFERENCE BTWN AT GROSS TAXI WT AND OVER GROSS IS ONLY ONE POUND. SINCE THE EXACT WT NUMBERS FOR ANY PARTICULAR SHIP IS KEPT IN A COMPUTER BY LOAD CTL; OR WT AND BAL; THE COCKPIT CREW WILL NEVER KNOW EXACTLY HOW MUCH THEY WEIGH PRIOR TO RECEIVING WT DATA FROM THE COMPANY. I THINK THE PROPER CORRECTIVE ACTION WOULD BE FOR DISPATCH TO HOLD THE FLT IF THERE IS ANY DOUBT; AND ACCEPT THE DELAY IN THE INTEREST OF SAFETY.