Dart assists Den in running The Sodor Dieselworks, Dart didn't works at The steelworks, but part of The Dieselworks works with Metal and foundry. Dart is very helpful to the Dieselworks, when Happy Hook was old and broken he was the first engine to complain. also, Dart can read Den's mind and he can quickly explain what Den is trying to say. Dart likes jokes, but he still get grumpy and irritable.
Dart is a 0-4-0 diesel-hydraulic shunter build by W. G. Bagnall.