Citation Excel (C560XL)
Air Traffic Control Fully Certified
Confusion; Situational Awareness
Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors
A C560 landed on Runway 01 and exited on Taxiway Q. A Gulfstream landed on Runway 01 after the C560 cleared the runway at Taxiway Q. Upon passing the hold short line; the C560 switched to Ground Control frequency and made a 'U' turn on Taxiway Q; back towards Runway 01. Upon seeing this; I immediately told the Gulfstream; who had touched down onto Runway 01 at this point; to stop. The Gulfstream came to a full stop between Taxiways D and F. Both aircraft exited Runway 01 and taxied to parking without incident. It should be stressed to pilots during their training and careers the importance of working together with ATC. Perhaps he was confused about the airport layout; but there is nothing wrong with asking for progressive taxi instructions instead of making poor decisions with dire consequences.
TEB Controller described a potential ground conflict when traffic exiting the runway initiated a 'U' turn toward the landing runway; the reporter directed a subsequent landing aircraft to stop on roll out.