B757 first officer reported a near collision with a bus while taxiing at ord.

Attributes
ACN	1347282
Time
Date	201604
Place
Locale Reference	ORD.Airport
State Reference	IL
Aircraft 1
Make Model Name	B757 Undifferentiated or Other Model
Flight Phase	Taxi
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 20000 Flight Crew Type 3482
Events
Anomaly	Conflict Ground Conflict Critical Ground Event / Encounter Vehicle

Narrative:

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.

Original NASA ASRS Text

Title: B757 First Officer reported a near collision with a bus while taxiing at ORD.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.