Me: Because Starlight Express!
I'd been told the story was "The Little Engine that Could" on roller skates. It starts that way but goes into much more... interesting places.
Frank Rich of the New York Times noticed as well. In his 1987 review he wrote:
"Andrew Lloyd Webber modestly explains that he conceived his new musical, ''Starlight Express,'' as an entertainment ''event'' for children who love trains. Over two numbing hours later, you may find yourself wondering exactly whose children he has in mind...
All the women are subservient carriages vying for the favors of mostly abusive male locomotives - with only an androgynous male caboose occupying lower social status. This hierarchical scheme is reinforced by Ms. Phillips's muscle-flexing choreography, seemingly inspired by male physical-culture magazines, and by the robotic costumes, which emphasize codpieces for the men and tight corsets and miniskirts for their groupies."