The EMD FL9 (New Haven Class EDER-5) 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. 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"). Design Due to concerns about diesel emissions in the East River Tunnels and the underground tracks of Grand Central Terminal and Penn Station, passenger trains entering New York City have long been required to use electrical power, as coal and later diesel exhaust would pose a hazard to human health in the confined underground spaces. At the same time, much of the New Haven's trackage was not electrified beyond New Haven. To allow passenger trains to travel to New York City from non-electrified lines without requiring a change of locomotives, the New Haven Railroad purchased a class of locomotive that could switch between diesel and electric power on the fly. EMD's answer was a new locomotive based on their existing FP9, but lengthened to accommodate additional equipment, such as a larger train heating steam boiler and third rail contact shoes. Due to the additional weight, the locomotive was equipped with a three-axle rear truck, giving it an uncommon B-A1A wheel arrangement. Flexicoil trucks were used due to this type of truck having more room for fitting the third rail shoes. For electric operation, the FL9 was capable of using either an over-running or under-running third rail by means of retractable shoes operated by pneumatic cylinders. The first 30 locomotives also had a small DC pantograph for use within New York City's Grand Central Terminal, where long gaps exist in the third rail because of the complex trackage that includes numerous railroad switches. For operation into the Pennsylvania Railroad's Pennsylvania Station, the FL9 used the Long Island Rail Road's third rail system. The electrical supply available from the third rail—660 V DC—was identical to the requirements of diesel locomotive traction motors, enabling a fairly easy conversion to a dual-power locomotive. A DC electric compressor provided air for the brake system until the diesel engine was started. Two batches of FL9s were built; an initial 30 (including the original test units 2000 and 2001, originally built with a Blomberg front truck, but later upgraded following testing) from October 1956 through November 1957 with