The "Tunnel Motor" is the most reconizable locomotive in America. The air-intake for the radiator is located down by the walkway along side the hood; all other locomotives have their air-intake up on the roof. The SD40T-2 was built between 1974 and 1980; 312 were built. Southern Pacific, Cotton Belt (SSW) and the Denver & Rio Grande were the only three railroads to purchase the "tunnel" version.
The SD45T-2 production went from 1972 to 1975; 163 were built for SP and 84 weere built for SSW. The SD45T-2 had a longer hood for the V20, the SD40T-2 had the standard V16 diesel engine.
The large number of tunnels and snow sheds on Donner Pass and in the Rocky Mountains made is just what these olocomotives were made for. Seeing a tunnel motor in the Northwest was rare, but Southern Pacific did use them on their freights in and out of Portland. Occasionally one would show up on a Burlington Northern grain train.