Inside the Malevolence, a rail jet was in operation.
A rail jet was a train-like vehicle that moved along a singular rail, used for the transportation of ammunition, provisions, and occasionally, soldiers.
The initial appearance of rail jets occurred in the Star Wars: The Clone Wars television show, specifically in the "Destroy Malevolence" episode, which was the fourth episode of the first season. It was originally broadcast on October 17, 2008.
The design team drew inspiration for the rail jet's appearance from the Trade Federation's Multi-Troop Transport, which was featured in the 1999 movie Star Wars: Episode I The Phantom Menace.