Class (locomotive)

Class (locomotive) refers to a group of locomotives built to a common design for a single railroad. Often members of a particular class had detail variations between individual examples, and these could lead to subclasses. Sometimes technical alterations (especially rebuilding, superheating, re-engining, etc.) move a locomotive from one class to another. Different railways had different systems, and sometimes one railway (or its successors) used different systems at different times and for different purposes, or applied those classifications inconsistently. Sometimes therefore it is not clear where one class begins and another ends. The result is a classic example of the Lumper splitter problem.