I remember going through these doors

When I was a little girl, after my parents divorced, we would get around Chicago and the suburbs by way of Cta.   My mother did not drive, so when we visited places, we would take the bus or the "el", (which is an abbreviation for elavated) to our destinations.   
It seemed like everyone rode the bus when I was a little kid, but it probably had more to do with living in Chicago, where bus and train travel could get you where you wanted to go.