B737-700
Air Traffic Control Fully Certified
Confusion; Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown; Ground Incursion Runway
Air Traffic Control Issued New Clearance
Human Factors; Procedure
A B737-700 contacted me leaving the runway. I instructed him to hold short of Runway 22 on Taxiway Mike. He read back the hold short instructions. Ops 5 was conducting driver training at the time. Ops 5 requested to cross the from the west side of the airport to the east side of the airport. I instructed Ops 5 that they needed to cross at a different location. Ops 5 then moved to a crossing that did not require him to travel down the runway; only to cross the runway. I then coordinated my crossings with Local Control; and instructed Ops 5 to cross Runway 17 and to hold short of Runway 12R on H. I then gave instructions to numerous other aircraft. I then saw the B737-700 taxiing extremely fast and realized he was not going to be able to hold short of the runway. I saw a Super King Air 200 on departure roll and yelled for the B737-700 to 'STOP STOP STOP STOP.' After listening to the tape; the Ops vehicle had drawn out his response and had come back with his hold short again without using his Ops 5 ID; and apparently the B737-700 took Ops 5 instruction(s). I never instructed the B737-700 to cross Runway 22. I never heard him change his gate or hold short instructions; I believe due to frequency congestion. Driver training should be done at less congested times.
After landing in HOU; we told Ground we were parking at Gate XX. Told to taxi via M and hold short of Runway 22. After calling Ops; we called Ground changing the gate to XX. The next transmission both pilots heard was 'hold short of 12L at H.'  We readback clearance with our call sign. Both the Captain and I verified we were to hold short of 12L. Approaching Runway 22; another Controller told us to stop. We stopped but our nose was past the hold short line. Captain spoke to the Tower Supervisor after parking at gate. The Supervisor confirmed communication problems. Preventative Measures; ATC needs to confirm readbacks. All parties use call signs like we did.
HOU Controller described a runway incursion involving an inbound air carrier; the reporter listing communications problems and airport driver training as contributing to the event.