Railcar #4 was built over a number of years by volunteer Leon Weeks (pictured with the railcar, above). The car arrived for good to the Museum in 2010, and underwent a period of troubleshooting before it became operational. The vehicle has a 1931 Model T automobile engine, mounted on a brand new body. The railcar is modeled after an existing railcar, a former Sandy River & Rangeley Lakes RR track car, which went to Edaville RR and now resides at the Owl's Head Transportation Museum.
The railcar is used to haul passengers for trips that don't require a full sized train. It also operates in tandem with the normally scheduled train.
See the progress of work on the railcar here, on the Discussion Forum.