The LWT12, what stood for “Lightweight Train, 1,200 hp”, was a locomotive designed by EMD for hauling special, lightweight coaches. The idea was that a light train only required less engine power. Essentially, the LWT12 was a SW1200 switcher that had a streamlined aluminum body in the fashion of contemporary cars and only had a single, non-powered axle at the rear. The gear ratio was generally set for a top speed of 100 mph or 161 km/h, but in reality the top speed depended on the weight of the train.

The first of these was delivered to the Rock Island for use with their “Jet Rocket” train between Chicago and Peoria. The trainset was created from Talgo II cars where the cars were articulated on common single-axle trucks. Two more locomotives were built for promotional tours around the USA. They received ten-coach sets built from 40-feet GM Scenicruiser aluminum bus bodies known from the Greyhound lines. These sets were marketed as “Aerotrain”.

The two demonstrator sets were tested by several railroads which found out that they could barely reach speeds in excess of 80 mph or 129 km/h. Furthermore, they often needed helper locomotives on grades what stood in contrast to the economical lightweight train concept. Both demonstrator sets were sold to the Rock Island for a low price and used for commuter services until 1965. Today, these two locomotives and two coaches are on static display.