Problems of overheating in exhaust-choked Sierra and Shasta tunnels led EMD and SP in the early 1970s to develop the SD45T and its predecessor SD40T. The answer turned out to be simple and elegant: move air intakes from the top of the units to closer to cool air at rail level, a solution obviously not needed here on March 31, 1978, as a dwarf signal guides SP SD45T-2 9361 and its westbound freight through the El Paso, Texas, yards. The so-called “Tunnel motors,” were so successful that SP and its Cotton Belt subsidiary acquired 247 of the big units (almost 600 including SD40T’s) for use system-wide.
