Date: 201411
Local time of day: 1801-2400
Location: PDX.Airport, OR
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower PDX
Second aircraft: Light Transport; Low Wing; 2 Turboprop Eng
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Distraction
Second reporter function: Pilot Flying; Captain
Anomaly: Conflict Ground Conflict; Critical; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Rejected Takeoff
Contributing factors: Airport; Human Factors; Procedure
Primary problem: Procedure

Narrative: I was working Local Control. An [Air Carrier Jet] was ready for departure on RWY 10L. I scanned my runway and final and cleared [Air Carrier Jet] for takeoff. I watched [Air Carrier Jet] round the corner and begin takeoff roll; and I started writing down the hourly traffic count for the supervisor. I then heard the Ground Controller come running over and yelling 'HOLD DEPARTURES!!! HOLD DEPARTURES!!' I immediately keyed up and said '[Air Carrier Flight Number] STOP!' as I saw a [Twin Turbo-Prop] cross the hold lines onto RWY 10L at the A4 intersection. '[Air Carrier Flight Number] responded '[Air Carrier Flight Number] go ahead' and it appeared they were backing off the throttle as they said that. I then said again '[Air Carrier Flight Number] Stop' and they started to brake more aggressively. (I have to take a moment here to say that I'm fully aware the correct phraseology in the 7110.65 is 'cancel takeoff clearance.' I learned a valuable lesson when I worked at my last facility; we had a LOT of new and foreign pilots that had a hard time understanding English. Sometimes the correct phraseology takes too long; or is too confusing in a dire situation. So I guess I made an unconscious decision in the split second I had that this situation called for immediate action; and that action was for [Air Carrier Flight Number] to stop; so that's what I said; and it worked.) I saw that [Air Carrier Flight Number] was going to be able to stop in time before getting to the A4 intersection. I then thanked [them] for making the quick stop and explained that there was a [Twin Turbo-Prop] at A4 that had started to taxi onto the runway.There have been several of the same type of incursions [at A4 intersection] in the past. Ground Control is across the tower cab from the GA ramp. We make it a priority to keep an eye on aircraft exiting the ramp onto taxiway alpha; but with ground's workload and having to pass strips to both locals on either side of the tower cab it is difficult to delay other ground operations so you can keep an eye on aircraft turning that corner. We currently have this area designated as a hotspot. I have to say; as scary as this situation was; the system did work. Ground Control kept an eye out and we caught it in enough time to correct the situation.


Second narrative: We were cleared for takeoff on runway 10L at Echo by PDX Tower. After takeoff thrust was established; but prior to 80 knots being called; we heard Tower say '(flight number) Stop'. I queried my First Officer and he said Tower said 'Stop; I think there is something on the runway.' With light rain and overcast skies; it was difficult to see the aircraft downfield. I immediately; performed the rejected takeoff procedures and came to a complete stop. In the meantime; Tower had repeated their call for us to stop. It became clear that a [Twin Engine Turbo-Prop] downfield at A4 had crossed the line and was now backing up to get behind the line.


Synopsis: Medium Transport flight crew rejected takeoff below 80 knots when directed to 'stop' by the Tower due to another aircraft on the runway.