AN ACR B737 ON TKOF ROLL ON RWY 30L SAW AN ACR DC9 TAXI ACROSS THE ACTIVE RWY. CAPT FLYING THE B737 ROTATED 15 KTS EARLY AND PASSED OVER THE TOP OF DC9 BY 100-150 FT. FLC ATC REVIEW INDICATES IT WAS A SYS ERROR.

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OUR ACFT WAS CLRED FOR TKOF ON RWY 30L AT HOU. DURING ACCELERATION WE NOTICED A DC9 TYPE ACFT TAXIING WBOUND ON TXWY H. AS WE CONTINUED OUR TKOF ROLL; IT BECAME EVIDENT THAT THE DC9 WAS GOING TO PENETRATE OUR TKOF PATH ON THE RWY AND AN EARLY ROTATION WAS MADE TO AVOID COLLISION WITH THE DC9. (DUE TO OUR SPD; WE WOULD HAVE BEEN UNABLE TO STOP AND OUR ONLY CHOICE WAS TO ROTATE.) WE MISSED THE DC9 (NOW CTR OF RWY 30L) BY AN ESTIMATED 100-150 FT VERTLY. OUR UNDERSTANDING WAS THAT SOMEHOW TWR CLRED US FOR TKOF AND GND CTL CLRED THE OTHER ACFT TO TAXI ACROSS OUR RWY! SUPPLEMENTAL INFO FROM ACN 347081: I KNEW THAT WE HAD TO GET AIRBORNE. I TOLD THE FO THAT I'M ROTATING; AND DID AT ABOUT 15-20 KTS BELOW ROTATE SPD AND FLEW OVER DC9 AT APPROX 100-150 FT AGL. CTL ERROR APPEARS TO BE THE CAUSE AFTER TALKING TO THE SUPVR INVESTIGATING THE INCIDENT. I'M ALSO GLAD THAT WE WERE USING FLAPS 5 DEGS FOR TKOF INSTEAD OF FLAPS 1 DEG. ANOTHER CONTRIBUTING FACTOR I THINK WAS THAT THE PLT OR MECH THAT WAS TAXIING THE AIRPLANE DID NOT CHK FOR TFC ON THE RWY PRIOR TO XING IT.