Why do railroads use catenary?

When you think about electrified rail lines today, the first thing that probably comes to mind is Amtrak’s Northeast Corridor. But in the first half of the 1900s, before the start of the diesel era, railroads used electrified lines to move freight and passengers. Examples in the east included the New York, New Haven & Hartford; Pennsylvania RR; and Virginian Ry. The west end of the Great Northern and Milwaukee Road both had electrified mains as well. All of these lines have one thing in common. Catenary. So why do railroads use catenary?

Catenary is a means of getting electricity from overhead lines to pantograph-equipped electric locomotives (and interurbans, streetcars, and light rail vehicles). You can learn more about catenary and other terminology related to electric trains in the infographic above from the November 2002 issue of Model Railroader.

Electrified routes have served different roles in different parts of the country throughout the years, which partially answers our question “Why do railroads use catenary?” In the east, electrified lines were used to support the high volume of freight and passenger traffic. In addition, electric trains filled a need when smoke abatement laws prohibited the use of steam locomotives in large cities.

In the west, electrified routes helped on routes with steep grades and long tunnels. In his book Great Northern Steam & Electric In Color (Morning Sun Books, 1999), David H. Hickcox wrote about the railroad’s strategy in the 1920s for conquering Washington’s Cascade Mountains. “A modern single-phase power system with a small fleet of new, more powerful electric locomotives would eliminate the problem of smoke, increase speed, allow for heavier trains, increase the flexibility of operations, and generally provide more efficient and less costly operations.”

Aging infrastructure and the efficiency of diesel locomotives spelled the end of many electrified routes. Great Northern ended electric operations in July 1956 after a new ventilation system was installed in Cascade Tunnel. Norfolk & Western pulled the plug on its former Virginian Ry. line in June 1962. Milwaukee Road ceased operations of its electrified lines in May 1974.

Today, Amtrak’s Northeast Corridor keeps the spirit of the New Haven and Pennsy electrified routes alive. The Iowa Traction Ry. and the Desert Power RR are the last two electric freight operators in the United States. Streetcars, light rail vehicles, and interurbans can be found under wire throughout the country.

The many faces of catenary

At first glance, catenary may all look the same. However, that’s not the case. As I learned from retired professional railroader and noted HO scale modeler Rick Abramson, the New Haven used three types of catenary. In addition, he noted there are different classes of catenary. “Compound catenary has (from top to bottom) the primary messenger, the secondary messenger, and the trolley contact wire,” Rick wrote in Model Railroading: The Ultimate Guide 2023. “Simple catenary has just the messenger and trolley.”

Now that we have a pretty good grasp on the question “Why do railroads use catenary?” we’ll next look at some of the different ways railroads supported the wires. Wood poles were common on the GN and Milwaukee Road. Electric units on the Pennsy and New Haven rolled under steel bridges, many of which still stand on the Northeast Corridor today. Though not a major player in the world of electrified railroading, the Detroit, Toledo & Ironton used a series of 365 concrete arches to support catenary on its Dearborn Branch, as shown in the photo above.

Practical application

When I hear “catenary” one of the first model railroaders I think of is Rick Abramson. His HO scale New York, New Haven & Hartford layouts have appeared in the August 2004 MR, Great Model Railroads 2020, and Model Railroading: The Ultimate Guide 2023.

Rick’s New Haven model railroads have all featured the railroad’s floating beam catenary. He modeled simple catenary, which features a messenger and trolley, as it was easier to install and maintain than compound catenary. “Installing catenary is an exacting and time-consuming process,” Rick wrote in GMR 2020. “The wire can’t deviate from side to side any farther than the distance between the end horns of the pantograph shoe that makes contact with the trolley wire.”

Though the catenary on Rick’s layout is well executed, it’s non-functioning. “Since I was using brass catenary bridges, I opted not to power the wire due to insulation issues,” Rick noted in The Ultimate Guide. “Even if the wire was powered, visitors and operators probably wouldn’t notice. A 12V arc isn’t quite as illuminating as an 11,000V AC arc!”

Catenary on your model railroad

Scratchbuilding catenary isn’t for everyone, but there are off-the-shelf products to make the job a bit easier. Model Memories offers a variety of HO scale items for re-creating catenary based on New York, New Haven & Hartford; Pennsylvania RR (PRR); Milwaukee Road; Great Northern; Virginian; Chicago, South Shore & South Bend; and Northeast Corridor prototypes. The manufacturer also offers O scale catenary supplies based on those used by the New Haven and PRR, as well as pre-formed wire sections.

Here are some other companies that produce catenary products. Though the catenary is somewhat interchangeable, some of the masts produced by these companies may not match prototypes used in the United States.

• Kato USA Inc. (N scale)
• LGB (large scale)
• Märklin (Z and HO scales)
• Peco (HO scale)
• Viessmann (N, HO, and TT scales)