Dart is a small diesel engine who is one of the recent purchases for the North Western Railway. He works in the Diieselworks alongside Den and to help him finish his sentences. He hates Paxton for some reason.
Dart along with Fergus and Daisy are some of the new engines purchased for the railway in the beginning of inheritance. His primary Job is to work with Den at the Dieselworks and to help others understand what Den is saying if his speech is not understandable. After S.C.ruffy has perished he and Den had noticed that no one had been arriving to the Dieselworks due to the lack of accidents that followed S.C.ruffy's demise.