If a railroad locomotive is an iron horse, then a vast herd of them has been put out to pasture in Salt Lake City.

They’re lined up, nose to tail, waiting to go nowhere — at least for now. By some estimates as many as 200 railroad engines — each one costing about $3 million — have been sidelined over the last year or so in a Union Pacific rail yard just north of downtown Salt Lake City.

And it has nothing at all to do with the new coronavirus.

A company spokeswoman for Union Pacific refused to answer detailed questions about the unusual sight, but Kristen South wrote in an email to the Deseret News that the engines are “being stored” due to a companywide efficiency program that kicked in during 2019.

To the labor union representing Union Pacific’s engineers and conductors, the idling of so many powerful engines highlights an ongoing threat to jobs and a growing concern about railroad safety.

“They’re basically doubling the size of trains, so they don’t need as many locomotives,” said Jay Seegmiller in a trackside interview. He’s the spokesman for SMART-TD, the transportation division of the International Association of Sheet Metal, Air, Rail and Transportation Workers.

Union Pacific refused multiple requests for an interview and would not reveal how many locomotives are idled in Salt Lake City. Using an aerial drone survey of the trains, it’s estimated there were at least 150 engines parked just east of I-15. They’re lined up on several parallel tracks stretching from around 900 North to 1800 North.

Seegmiller and a Union Pacific engineer who requested anonymity said they believe the actual number of engines is about 200.

Union Pacific confirmed that each locomotive costs about $3 million, suggesting that hundreds of millions of dollars worth of hardware is sitting unused, just in Salt Lake City.

The company’s financial reports show that, nationally, the company sidelined 3,100 locomotives by the end of 2019. That’s about 40% of the company’s engines. It’s a normal part of the railroad’s operation to keep some locomotives “in storage”; the stored engines are waiting and ready to respond to fluctuations in the rail business.

But lately there are many more idle engines than usual because of a new strategy to collect freight cars more efficiently and group them into longer trains using fewer locomotives.

It’s part of an industrywide effort to raise the profitability of railroads through an approach known as “precision scheduled railroading.”

The strategy “keeps inventory and supply chains moving,” South wrote, because it “shifts the focus from moving trains to moving cars. This allows us to reduce the number of times a car is touched to best serve our customers and get their goods to market as quickly as possible.”

Another result, Seegmiller said, is that trains are getting far too long.

“Two, three, four miles (long), depending on the equipment,” he said.

Writing for the company in an email to the Deseret News, South said Union Pacific’s average train length increased only 16% “as a result of efficiency gains made through Unified Plan 2020.” However, she didn’t dispute Seegmiller’s claim that some trains stretch up to four miles in length.