Why railroads run locomotives in the same direction

If you’re new to the hobby, your journey is probably similar to mine. Your first exposure to trains was probably Thomas the Tank Engine, or a relative taking you to a local train show. Whatever the case may be, as you mature in your interest, you’re bound to have a lot of questions about why railroads do – and don’t do – certain things. When I began exploring the ins and outs of railroad operations as a teenager, a lingering question piqued my curiosity. “Why are some trains powered by locomotives all facing the same direction, while others have them facing differently?” The answer is quite simple once you understand how multiple locomotives work together.

Most North American locomotives today are diesel-electric, meaning that they’re essentially electric vehicles with onboard power generators fueled by diesel. The engine powers the generator, which in turn powers the electric motor on each axle. A group of locomotives works together using a set of 27-pin connector cables that transmit electric power between each one, ensuring synchronization from the lead to the trailing unit.

Known as Multiple Unit control – “MU” – this technology was created by Frank J. Sprague in 1896, specifically for the elevated railways of Chicago. It soon became the norm on electric rapid transit systems worldwide as cars could be coupled together from either end, eliminating the need to turn them at destination points. The concept overtime was adopted by locomotive builders in the 1920s and 1930s to meet horsepower requirements for heavy freight trains since early diesel-electrics were nowhere near as powerful as steam locomotives. Plus, since each steam locomotive needed its own two-man crew to operate, diesels MUing allowed railroads to operate longer trains with fewer crewmen.

Reading 4-8-4 steam locomotives Nos. 2124 and 2100 double-head the Iron Horse Ramble excursions. Karl Zimmermann photograph

In the steam days, each locomotive had to face the same direction when double heading because radio technology was not widely used until the late 1940s. Trains were instead operated using hand signals and whistle blasts to confirm movements or speed changes. At each destination, the steam locomotives had to be spun on a turntable or “wyed” so they would face the forward direction for outbound movements. With both or more facing the same way, communication could be seen and heard by the crew. This method wasn’t foolproof as the complicated signals were misinterpreted. MU’d diesels eliminated those signals, cutting out any potential miscommunications.

Unlike a steam locomotive, diesels could also operate “back-to-back” with a cab facing in either direction. With an MU-equipped cab unit (or “A Unit”) on each end, yard crews did not need to turn them, saving the railroad time and money. Many railroads elected to remove their remaining turntables during the transition from steam to diesel in the 1960s, leaving only wyes at strategic locations. Since diesels were more versatile and not limited to specific territories or subdivisions, an additional forward-facing locomotive could be added to the consist in the event the lead unit of a train was facing the wrong direction for its next assignment.

Although MU capabilities essentially eliminated the need for turning locomotives, antiquated union agreements from the steam era often prohibited railroads from realizing the technology’s full potential. Many contracts stipulated that any locomotive without bidirectional controls must face forward. In the event there weren’t any available diesels facing forward to lead the train, the railroads had to obey union contracts by turning them. They also had to pay each crewman a claim against their contract for not supplying the appropriately-facing motive power.

Southern Railway No. 2783 leads a freight train toward two targeted signals. Curtis C. Tilotson Jr. photograph

In order to save money on these claims, some railroads got creative. One solution was to equip locomotives with dual-control stands to make them truly bidirectional with either end acting as the “front.” Though an up-front cost, it saved time in the yard and eliminated any union claims. Southern Railway’s approach to bidirectional operations was to make the short end of the unit the rear while having the engineer on the right-hand side with the long hood leading. In the event a locomotive was running in “reverse,” the engineer would be on the left side but with a short hood so his forward vision to the right side wasn’t impaired.

High short hood locomotives were initially the standard on all first-generation EMD locomotives. But with the introduction of the SD24, EMD gave its customers the option for a low short hood. Norfolk & Western Railway and Southern were the only holdouts. Since most of their locomotives were operated long hood forward, it’s a common misconception that they were set up for additional crew safety in the event of a collision. While that might have been a secondary benefit, the real reason was bidirectional-operation capability. As the union contracts were renewed under new terms, and with the advent of “comfort cab” units in the late 1980s, such operating practices became impractical. It’s now rare to find vintage ex-N&W or ex-Southern units running long hood forward on Norfolk Southern.

While you won’t often see modern diesel locomotives running “backward” in the lead position on a mainline freight train today, you will frequently see them running “elephant style.” In other words, multiple units facing nose-to-tail instead of back-to-back, the same as a herd of elephants. Because modern locomotives can be MU’d together from either end, it’s often easier to run outbound power as-is, whether elephant-style or otherwise. That is the main reason why you see locomotives running in the same or different directions. However, no matter how they are placed, the synchronized operation of the locomotives MU’d together is unaffected.

Three CSX diesel locomotives run “elephant style” with the Ringling Brothers circus train out of Charleston, West Virginia on May 8, 2017. Ryan Markham photograph