A320
Flight Crew Air Transport Pilot (ATP)
Distraction; Workload; Communication Breakdown; Confusion
Ground Incursion Runway
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance
Procedure; Human Factors; Airport
We taxied out for takeoff on Runway 15L as usual. While completing the 'Before Takeoff Checklist' the First Officer answered a call to line up and wait Runway 15L. I did not hear the call since I was speaking as part of a checklist response. I waited to see if his readback would be questioned and it was not; so we taxied into position. [Runway] 15L was a departure only runway and therefore no chance of an incursion; however 40 seconds later; another aircraft questioned the Tower if they should position and hold; or not. Tower instructed them to do so and told us to taxi down and exit the runway. I must assume that we answered someone else's call and that we entered the runway in error. Nothing more was said and we took off shortly thereafter.I don't think our error caused any distress to anyone; however; it could have in a different situation. The First Officer was fairly new to the airline and somewhat nervous. He was also very task saturated due to the highly complex IAH ground procedures and short taxi. The ground procedures at IAH seem unnecessarily complicated. Ramp to push and turn around; Metering to get to Ground Control; every taxiway in Houston has a 4 syllable name; and then Tower; all within 300 yards. LGA handles twice as much traffic with 2 frequencies. I will be more leery of accepting clearances I did not hear personally in the future; however; I really think IAH should examine their procedures.
The flight crew of an A320 mistakenly responded to a line up and wait clearance intended for another aircraft and was asked to vacate the runway for the intended recipient. The Captain reporter cited excessively complicated ground movement procedures at IAH; a short taxi to Runway 15L and an inexperienced and overtaxed First Officer as contributing factors.