Technical specifications of locomotives often include tractive effort curves, which show the relationship between tractive effort and velocity.
The basic shape of the graph is shown schematically (diagram right). The line AB shows the operation at the maximum tractive effort, the line BC shows the relationship of continuous tractive effort being inversely proportional to speed.
Tractive effort curves will often have graphs of rolling resistance superimposed on them—the intersection of the rolling resistance graph and tractive effort graph gives the maximum velocity (i.e. when the net tractive effort is zero).
Read more about this topic: Tractive Force
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