Originally Posted by
threeoh
The 24/7 landside bus that replaces the people mover (ATS). You should be able to pick it up on the lower level of T5 but check for signs. There's one that circulates to the terminals (which is what you want) and another that goes to remote parking.
The
Transportation Between Terminals page on ORD website confirms this and further indicates busses arrive every 5-15 minutes. The page also has a
map of shuttle bus service routes.