The 44-tonner was a workaround. In 1937, seeing that new diesels were putting the fireman's role in jeopardy, the railroad unions negotiated the "90,000 Pound Rule" with the railroads - specifying that any engine with a weight on drivers of 90,000 pounds or more would require a two-man crew. General Electric's 44-tonner, introduced in 1940, skirted the 90,000 pound rule and was thus the largest locomotive that could legally be operated by one person on a common carrier railroad.