On Tuesday, February 17, 2015, at 2145 central standard time, an Embraer E145, N698CB, operated by American Airlines Group as ENY3084, was on takeoff roll on runway 28R from intersection EE at the Chicago O'Hare International Airport (ORD), Chicago, Illinois. A Canadair Regional Jet CRJ-700, N154GJ, operated by GoJet Airlines as GJS3710 was taxiing to runway 28R via taxiways F and N. GJS3710 did not turn left at taxiway N as instructed and instead entered runway 28R and made a left turn toward the departing ENY3084. According to the pilot of ENY3084, he maneuvered to avoid GJS3710, and continued his departure. ENY3084 was a regularly scheduled flight from ORD to Port Columbus International Airport (CMH), Columbus, Ohio. GJS3710 was a regularly scheduled flight from ORD to the Lester B. Pearson International Airport (YYZ), Toronto, Ontario, Canada. Both flights were operating under the provisions of Title 14 Code of Federal Regulations Part 121. Night visual meteorological conditions prevailed, and no injuries were reported on either flight. ENY3084 was departing ORD from runway 28R at the taxiway EE intersection and had been cleared for takeoff. GJS3710 was on the outbound taxi from taxiway H to U to F to N to taxiway EE. According to recorded Airport Surface Detection Equipment, Model X (ASDE-X) data, ENY3084 began departure roll at 2145:17. GJS3710 was about 265 feet north of the runway 28R edge line, taxiing south on Taxiway F at approximately 11 knots. At 21:45:28, an ASDE-X alert was issued when ENY3084 met the velocity and acceleration parameters that are required by the ASDE-X to be considered a departure. ENY3084 was traveling at approximately 56 knots and was approximately 1041 feet from the runway 28R/taxiway F intersection. GJS3710 was on taxiway F approximately 42 feet from crossing the runway 28R edge line and was traveling at approximately 11 knots. At 21:45:30, ENY3084 was about 831 feet from the runway 28R/taxiway F intersection, traveling about 66 knots. GJS3710 entered runway 28R traveling at about 11 knots and turned east toward ENY3084 before coming to a stop on the north side of Runway 28R at taxiway F. When GJS3710 entered the runway from taxiway F, an aural alert of "Warning Runway Two Eight Right Occupied" was voiced in the tower and the corresponding alert text "RWY 28R|ENY3084, GJS3710|RWY OCCUPIED" was displayed on the ASDE-X displays. According to the flight crew of ENY3084, they were traveling at about 100 knots when they first observed GJS3710 enter the runway and stated they maneuvered the aircraft to the left of centerline to avoid a collision. According to the pilot of GJS3710, after he realized that he had missed the turn to taxiway N and had entered runway 28R, he made an immediate left turn and saw what looked like an Embraer 145 aircraft taking off. He stated he turned his aircraft to face the departing aircraft in order to present the lowest profile. His primary concern was keeping the tail section of his aircraft away from the runway centerline. He recalled that the centerline of his aircraft was on the north side of the painted runway edge, so only the right half of his aircraft was on the runway proper. He saw the nose gear of the Embraer and recalled seeing the main landing gear of the Embraer come off the ground as the Embraer passed his aircraft. He estimated that the aircraft wingtip to wingtip clearance had been 15-20 feet. At 21:45:36, ENY3084 passed GJS3710 on runway 28R. The ASDE-X could not resolve the minimum separation distance. The positional accuracy of the ASDE-X is +/- 20 feet. GJS3710 then exited runway 28R at taxiway P. The pilot of GJS3710 called his flight dispatcher and then the tower supervisor to discuss the event and then continued the flight to CMH. Airport Surface Detection Equipment Model X The air traffic control front-line manager on duty in the tower stated that the airport surface detection equipment, model X (ASDE-X) alarmed; however, there was insufficient time to cancel ENY3084's takeoff clearance. The distance between taxiways EE and F was approximately 1,900 feet. ASDE-X data for this investigation was obtained from the Federal Aviation Administration. Figure 1 shows the ASDE-X presentation just prior to ENY3084 starting takeoff roll. Figure 2 illustrates the ASDE-X presentation as GJS3710 is approaching runway 28 on taxiway F. Figure 1 – ASDE-X presentation of ENY3084 and GJS3710 at 2145:13. Figure 2 – ASDE-X presentation of ENY3084 and GJS3710 at 2145:27. Weather Information The 2051 Aviation Routine Weather Report (METAR) observation for ORD reported wind 290 degrees true at 12 knots with gusts to 18 knots, visibility 10 statute miles. Few clouds at 3,800 feet above ground level (agl), scattered clouds at 12,000 feet agl, and broken clouds at 15,000 feet agl. Temperature minus 11 degrees Celsius (C), dew point minus 18 degrees C, altimeter 29.88 inches of mercury. Federal Aviation Administration Air Traffic Control Service Duty Priority FAA Joint Order (JO) 7110.65(V), Air Traffic Control, paragraph 2-1-2 addresses an air traffic controller's operational duty priority and stated [in part]: a. Give first priority to separating aircraft and issuing safety alerts as required in this order. Good judgment must be used in prioritizing all other provisions of this order based on the requirements of the situation at hand Team Position Responsibilities FAA Joint Order (JO) 7110.65(V), Air Traffic Control, paragraph 2-10-3 addresses air traffic control tower team position responsibilities and stated [in part]: c. Primary responsibilities of the Tower Team Positions: 1. Tower Position(s) (LC or GC) (a) Ensure separation (b) Initiate control instructions (c) Monitor and operate communications equipment