Nelson is a ballast tractor who works for the Sodor Construction Company. Nelson's job is to haul members of the construction team and the Pack to and from work. As the bearer of such weighty loads, he often feels overworked, but never complains. In his first appearance, Jack asked Nelson if he was the most important, as Patrick boasted that he was the most important earlier. Nelson told Jack that he is the most important, as he is the main source of transportation. Later, when a fierce storm ra