You can get rid of the cleaning staff right now. The terminals will become disgusting and people will stop using them. There is no way around this type of overhead. If you have larger numbers of people passing through, you need cleaning and maintenance.

Your original point isn’t even true - in California there is constant maintenance of the road network and crews of community service workers doing their sentence cleaning trash on the highway shoulder.

Roads still have far fewer staff per mile than railways, however you measure.

In turn, that makes them cheaper.

Lol, that depends heavily what you consider staff. E.g. look at freight, if you move cargo by trucks you need 1 staff member (sometimes called drivers) per truck. Train on the other hand needs only 2 people per hundreds of meters of train...

Even worse for individual car transport. You need one staff (driver) per vehicle...

Is there a source for this? Is this source heavily context-dependant?