Definition of "handcar"

Yours goes up and mine goes down / and then we do it the other way around. / Don't you give me that sigh, cause if we can't see eye-to-eye / then our missions will be always filled with strife, / cause a handcar is a metaphor for life.

2013 March 1, “Sidetracked”, in Phineas and Ferb, season 4, episode 5, spoken by Agent Lyla (Samantha Bee)

A small handcar rested on the tracks, its iron pump waiting for a human touch to animate it.

2016, Colson Whitehead, The Underground Railroad, Fleet (2017), page 306