The EMD SDP45 was a six-axle C-C 3,600 hp (2,700 kW) diesel locomotive built by General Motors' Electro-Motive Division of La Grange, Illinois. It was fundamentally a passenger-hauling version of the SD45 on a stretched locomotive frame and with an extended long hood at the rear, aft of the radiators, giving space for a steam generator for passenger train heating. The end of the long hood on steam generator-equipped units was squared, unlike the pointed end of the regular SD45. The Erie Lackawanna Railroad ordered a number of SDP45s for freight service purely for their longer frames that permitted a larger fuel tank, which gave the locomotives the greater range the EL was looking for. These units had a pointed long hood end; the extra space aft of the radiators was empty. The Southern Pacific Railroad used their SDP45s for commuter service on the San Francisco Peninsula after Amtrak took over long-distance routes in 1971. SP's commuter service was very demanding work and the locomotives required electrical modification in order to meet those demands. They stayed on the commute route until 1985 when Caltrain equipment arrived, and they were placed into freight service until their retirement. One SDP45 built for the Burlington Northern Railroad was retrofitted with a radial four-axle truck by EMD, converting it to a A1A-D wheel arrangement. The middle traction motor in the lead truck was removed. This testing paved the way for the HTCR three-axle radial truck first seen under SD60 EMD 3, SD60MACs, and made standard on the early SD70 series.