Date: 201808
Local time of day: 1201-1800
Location: ORD.Airport, IL
Flight conditions: VMC
Aircraft: B757 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Second aircraft: Regional Jet 200 ER/LR (CRJ200)
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion
Second reporter function: Pilot Flying; Captain
Anomaly: Conflict Ground Conflict; Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; Flight Crew Took Evasive Action
Contributing factors: Aircraft; Airport; Human Factors
Primary problem: Airport

Narrative: We were at Bravo South taxiing out of the ramp at ORD. Ground Control issued us instructions to taxi to 28R/N5 via left turn on A; right turn on A9.K.CC.N then hold short of T on N. Neither I nor the captain have flown into ORD recently so we took a few moments to orient ourselves with the intended taxi route before the Captain released the parking brake and began taxiing. As per our taxi instructions; the Captain initially turned left onto taxiway A then right onto A9 where we noticed a CRJ200 rapidly approaching from the right on Taxiway B. Due to aircraft positioning and structural limitations (window frames); we were unable to see the CRJ until we had almost completed the turn onto Taxiway A9. The Captain firmly applied the brakes and both we and the CRJ came to a stop. As I was trying to contact Ground Control to clarify the taxi instructions; the CRJ passed in front of us (with plenty of room) and an additional aircraft behind him also passed. During the abrupt stop; [a] Flight Attendant (FA) slipped on some water in the aft galley; fell and sprained his ankle. He initially informed us that he was able to complete his duties so we continued taxiing for takeoff. About 15 minutes later we were informed that [the] FA's foot was swelling up and he would need medical attention. The Captain immediately initiated a gate return and we contacted Operations to get a gate assignment; FA supervisor and wheelchair for him. Coincidentally; while taxiing out for the continuation of our flight; the exact same thing happened again. We were cleared to exit the South Port and onto A9 only to find two aircraft rapidly approaching from the right on Taxiway B. This time; we were much more aware of the possible incursion at this location and the Captain was able to stop the aircraft gently.


Second narrative: I called ORD ATC Supervisor/Dispatch/Operations Manager to convey what happened. We departed the gate with new release (and it almost happened again at A9. We stopped with normal braking and asked [the] controller to who was to give way. We were told to give way to 2 RJs and continue). I was moving between 5-7 knots during the heavy braking event as I was in a turn. We did pause for 15-20 seconds after receiving taxi instructions to review their complexity. We did not notify ATC of our delay.


Synopsis: B757 flight crew reported a taxiway conflict necessitated braking aggressively; causing injury to a Flight Attendant.