B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 20000; Flight Crew Type 3482
Situational Awareness
Conflict Ground Conflict; Critical; Ground Event / Encounter Vehicle
Flight Crew Took Evasive Action
Human Factors
After our push back was complete; we began our initial taxi from [the] gate. I cleared the right side of the aircraft and verbalized 'all clear'. The push back angled the airplane requiring a turn to the left. As we began moving; I noticed what looked like the employee bus driving at a fairly high speed on the service road paralleling the terminal. It didn't appear that he was stopping (or even slowing down). I told the Captain to 'stop'. The arc of the wing during the turn would have most certainly hit the bus. I immediately called the Flight Attendants to ensure no one was injured and notified the ramp of the incident. The bus came to a stop close enough for us to see the bus number which we reported to the ramp.
B757 First Officer reported a near collision with a bus while taxiing at ORD.