EMD FL9

The EMD FL9 is a model of electro-diesel locomotive, capable of operating either as a traditional diesel-electric locomotive or as an electric locomotive powered from a third rail ("dual power"). Sixty units were built between October 1956 and November 1960 by General Motors Electro-Motive Division for the New York, New Haven and Hartford Railroad (the "New Haven"). The locomotives were designed to allow diesel powered trains to enter Grand Central Terminal, where non-electric locomotives are forbidden.

The FL9s were additionally intended to allow for the retirement of electric locomotives by the New Haven and the dismantling of electrification to save money. Only the electrification on the Danbury Branch was actually dismantled, negating a key reason the locomotives were purchased. However, the FL9s did make it possible for trains serving non-electrified lines to continue to Grand Central without stopping at New Haven, Connecticut, to switch locomotives.

The FL9s continued in passenger and occasional freight service under the New Haven's successor Penn Central, expanding their range to the Harlem Line and the Hudson Line in New York State. Conrail succeeded Penn Central in 1976 and sold 12 units to Amtrak for use on the Hudson Line. Its remaining units went to Metro-North Railroad in 1983, some purchased by the Connecticut Department of Transportation (CTDOT). Amtrak, Metro-North, and CTDOT all sent FL9s for rebuilding to extend their service lives.

Amtrak retired its FL9s in the late 1990s when new P32AC-DM locomotives that replicated their role entered service. Metro-North began replacing its FL9s in 1995 with new P32AC-DM locomotives, restricting them to branch lines in 2001. The remaining FL9s were no longer capable of third-rail operation due to their advanced age. New locomotives allowed for the final FL9s owned by Metro-North and CTDOT to be retired in 2009. More than 20 FL9s have been preserved at museums or with private owners; several remain in operation.