Rusty is a diesel engine who does maintenance work and odd jobs on the Skarloey Railway.
Rusty has always been a helpful little diesel. He has mostly been seen clearing lines, and doing other railway maintenance work. In the fourth season, Rusty helped saved Stepney, who was stranded on a siding in a scrapyard on the Other Railway, from scrap. When the Boulder went loose at the Quarry, Rusty narrowly escaped his own destruction after being chased by the giant stone. Along with Skarloey, Rheneas, and Elizabeth, he saved the Skarloey Railway from abandonment. Rusty once saved Duncan from falling into a river from an old bridge.
One Christmas, when Duncan began complaining more than ever, Rusty had the idea of telling the Thin Controller, who devised a plan. Rusty later saw Duncan lose his temper with Luke, who was blocking the track in front of him. But when Duncan felt sorry and helped Luke carry on his way, Rusty saw this too and told the Thin Controller.
He is currently working at the Skarloey Railway, along with the other narrow gauge engines.
Rusty is a trusty, tame, friendly little diesel. He is a dedicated worker, often maintaining the line, while understanding and respecting the importance of his duties. He also has a rather distinctive two-tone horn. Rusty is quick to remind others with regards to proper conduct, particularly Duncan, who was initially very suspicious of the little diesel. But despite their arguments they both seem to make amends in the end, because of how kind and tolerant Rusty is. He has a good working relationship with both Skarloey and Peter Sam in particular. Caring, calm, and quick-thinking, Rusty is modestly a credit to the Skarloey Railway.
Rusty is based on the Talyllyn Railway's Midlander, a Ruston Hornsby diesel, Unlike his basis, Rusty was never fitted with a different shaped radiator.
Rusty is painted orange with yellow lining and white lettering.