The EMD BL2 is a model of diesel-electric locomotive built by General Motors Electro-Motive Division (EMD). A total of 59 units (including a single BL1) were built between 1947 and 1949. The BL2 was not very successful, as it was unreliable and occupied a gap between carbody and hood units which resulted in it suffering from the drawbacks of both designs. However, lessons learned from the BL2 were incorporated into EMD's next design, the GP7. History EMD's diesel program was well underway by the late 1940s thanks to the success of the company's F- and E-units. While the F-units in production were great for moving trains over the railroad, their full-width carbody made it difficult for locomotive crews to see to the rear of the locomotive while switching. This was considered an acceptable sacrifice for a mainline locomotive, which was expected to do little switch work, since the full-width carbody type was considered much more handsome and stylish. By 1948, competitors Alco, Baldwin, and Fairbanks-Morse had introduced road switcher locomotives, which used the narrow hood and full walkway of a switcher with a longer frame and the high-speed trucks of a road locomotive. These locomotives were successful at displacing steam from secondary services such as local and branch-line work. EMD developed the BL1, basing it on the F3 and using the same bridge-truss carbody construction as the F-unit (as opposed to the weight-bearing frame of a true road switcher like the Alco RS-1) with the body cut away behind the cab to provide visibility to the rear. The first BL1 was EMD Demonstrator #499, built in September 1947. The BL1 Demonstrator was EMD Project 89499, thus the 499 Demonstrator number. The BL in the model name stood for "Branch Line", indicating that EMD felt the locomotive was best suited for light traffic and frequent switching chores. The BL1 was built with a light-weight underframe and draft gear and no multiple unit (MU) capabilities, as it was expected to operate as a single unit. However, MU capability was later added to the BL1. In response to feedback from the railroads, the visually-identical BL2 was built with a heavier frame and draft gear and MU capability. The production BL2 used the standard electro-hydraulic governor and notched throttle as used in the F3 (as opposed to the air-actuated throttle with which the BL1 was originally built). The BL2 could be equipped with a