EMB ERJ 135 ER/LR
Air Traffic Control Fully Certified
Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Air Traffic Control Issued New Clearance
Human Factors
An E135 was taxiing to Runway 35R via Hotel; Papa; Golf and Delta. I then amended his taxi instructions to hold short of Delta on Golf so I could put an aircraft with a flow time in front. The E135 was then told to taxi to Runway 35R via Delta; cross Runway 29. The E135 read back the instructions as told. The E135 did not make the turn on Delta and continued straight on Golf and attempted to cross Runway 35R. A B737 was rolling down the runway and as soon as I realized what had happened I instructed the E135 to STOP. I then asked the E135 if he had crossed the hold short line and he was not sure. Watch your taxiways and runways at all times. Even when pilots read back the correct instructions that does not mean they will follow through. As soon as you look away a pilot can make a mistake and turn the wrong way.
Tower Controller described a probable runway incursion event when after responding correctly to a taxi clearance; the aircraft made a wrong turn and may have crossed the runway hold lines.