What is the singular possessive of railroad?

The B&O Railroad's tracks ran throughout the small town. (one railroad with singular possessive)

The railroads' officers were keen to expand rail service in the 1800s. (more than 1 railroad, and plural possessive. This also means that "officers" indicates groups of men, one group per railroad company, but here used as a generic plural, no possessive.)

The railroad's conductor got married. (One specific railroad as singular possessive for one specific conductor.)

The railroads' conductors were mostly single men. (plural possessive, plural railroad companies with plural conductors).