The 5,000 series cars are part of an effort to modernize the CTA's fleet of aging rail cars.
A six-car train was added Sunday and additional trains will be added.
The cars replace the 2,400 series cars which are 35 years old.
The new cars allow for smoother acceleration and braking providing passengers with a more comfortable ride.
The cars face the aisle which allows more room for riders with backpacks, strollers and bikes.