How To Model Railroad Operations Why railroads run locomotives in the same direction

Why railroads run locomotives in the same direction

By Drayton Blackgrove | April 5, 2023

Why do I see some trains with locomotives all facing the same direction, but others have locomotives facing in different directions?

Email Newsletter

Get the newest photos, videos, stories, and more from brands. Sign-up for email today!

Four yellow locomotives on train climbing hill
An eastbound Union Pacific train with all locomotives facing the same direction heading up Cajon Pass in California on Sept. 12, 2021. Bill Stephens photograph

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.

Black-and-white three-quarter angle photo of 4-8-4 steam locomotive in actionReading 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.

Above, head-on photograph of a black locomotive leading a long freight train forward the camera.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.

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

One thought on “Why railroads run locomotives in the same direction

  1. Steam locimotives have directional suspensions. The lead trucks have different suspensions from the trailing trucks and they can not run backwards as fast as forward. The Reading T-1’s you show above had a speed limit of 65 forward and 35 backward in R.Co. days. Naturally on Iron Horse Rambles on the New York Branch I clocked them at track speed of 75. There were always plenty of officials around and often a shop guy was on the engine so I guess the overspeed was allowed.

    Seaboard Air Line (now part of CSX) probably started the idea of running the engines “elephant style.” In 1940 they split their Florida trains into East Coast and West Coast at Wildwood FL. The road power made the cuts. With MU diesels, they wanted to split the power there as well but the 60 degree nose slope of an EMD E3 prevented nose-to-nose coupling. EMD produced the E4 which had nose MU and couplers that extended far enough to allow nose-to rear coupling. This way the power consist could be split with all the cabs pointed in the right direction.

You must login to submit a comment