SD40T-2 ''Tunnel Motor'' Locomotive
Denver & Rio Grande Western - Speed Lettering
Two Road Numbers Available!

photo by Nathan D. Holmes

"Tunnel Motor" locomotives were designed to operate efficiently inside tunnels or snowsheds due to the constant problem of overheating engines. The high horsepower locomotives generated exhaust fumes and heat which collect in the top of the tunnels. On 'normal' EMD locomotives, exhaust and radiator intakes are on top of the locomotive, and are therefore unable to cool the engine properly, resulting in limited power output, overheating and shutdown. "Tunnel Motor" units have special air intakes that collect the cooler air from the bottom of tunnels to avoid ingesting their own superheated exhaust gases from the roof areas of the bore. Diesel Tunnel Motors pull their fresh air in from vents near the lower rear of the hood. A larger radiator increases power output.

The EMD SD40T-2 was ordered by only two railroads, Southern Pacific and Denver & Rio Grande Western. When D&RGW bought Southern Pacific, keeping the latter's name, the railroad owned all the existing Tunnel Motors. Union Pacific later purchased the combined railroads and took over their locomotives. Some of these locomotives have now been given a clean paint of armour yellow, others simply received yellow "patches" with UP insignia on them.

001-N4004-1 Road Number 5371
001-N4004-2 Road Number 5351

001-N4004