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There are no federal regulations on key rail sensors

About 6,000 hot-box detectors are positioned along US rails

This photo taken with a drone shows portions of a Norfolk Southern freight train that derailed Feb. 3 in East Palestine, Ohio. (AP Photo/Gene J. Puskar)

The Feb. 3 Norfolk Southern train derailment in East Palestine, Ohio, which caused no deaths, has sparked a national conversation over rail safety — particularly as profits soar at major rail carriers

One sticking point has been the use of the wayside hot-box detectors. These are used to detect the temperature of wheel bearings on passing rail cars. There were about 6,000 of these detectors placed along U.S. rail tracks as of 2015, according to a study by the Association of American Railroads (AAR). 

The National Transportation Safety Board has pinpointed an overheated bearing as a critical contributor to last month’s accident. The train passed three hot-box detectors in the span of 30 miles before it derailed in East Palestine, according to the NTSB. Only one detector, right outside the Ohio village, recorded a “critical” high temperature. By the time the crew was alerted, it was too late to prevent an accident.

As a result of the derailment and ensuing toxic fire, East Palestine residents were forced to evacuate. The Environmental Protection Agency continues to sample the air and water in the impacted area. It stated on March 2 that testing suggests a “low probability” of release of the chemical dioxin, a known carcinogen that results from burning industrial products. 


In a Feb. 23 news conference, the NTSB’s head told reporters that she believed that the derailment may have been avoided had these detectors been placed closer together, which would mean increasing the overall number of detectors on U.S. rails. 

“Had there been a detector earlier, that derailment may not have occurred,” NTSB Chair Jennifer Homendy said at the conference. 

But, Norfolk Southern didn’t break any federal regulation around the use or maintenance of its wayside hot-box detectors. That’s because there aren’t any: The Federal Railroad Administration (FRA) has never proposed one. New legislation from a bipartisan group of senators could change that. 

Here’s what’s at stake.


What is a wayside hot-box detector?

Wayside hot-box detectors are on average placed every 25 miles along the U.S. rail network, according to an FRA report. They have been deployed since the 1970s, according to Allan Zarembski, director of the University of Delaware’s railway engineering and safety program.

Trains pass hot-box detectors, and other types of wayside detectors, as they move along to their destination. Hot-box detectors measure the temperature of the train’s bearings. When one of these detectors senses that the temperature of a component is far above ambient temperature, an alert is sent to the train’s crew.

Then, the crew may stop the train to inspect the car in question. One device to measure if the bearing is overheated is a stick covered in wax, according to a current train conductor. The crew member rubs the stick on the problematic component. If the wax melts, that means the component is too hot. (You can also simply smell or feel the heat from an overheated wheel.)

A Norfolk Southern train. (Photo: Jim Allen/FreightWaves)

In Norfolk Southern’s case, according to the NTSB, an alert to stop the train and inspect the rail car requires a temperature reading of at least 170 degrees above ambient. This temperature reading may seem high to a layperson, but Zarembski said this is a standard requirement. 

These detectors aren’t perfect. False alarms do happen, and they lead to the crew having to stop the train and back up other trains on the system needlessly. As trains stretch to nearly 3 miles long, inspections mean that conductors could be walking for an hour or more to inspect bearings. 

An overheated bearing doesn’t necessarily mean the train is set to derail, according to a researcher from MxV Rail, a research firm connected to AAR.

These complications aside, hot-box detectors have been key in slashing accidents and derailments. According to a 2017 AAR study, their use contributed to a 59% decrease in train accidents caused by axle- and bearing-related factors since 1990.

Use of heat detectors is up to industry 

Despite the efficacy of the detectors, the federal government has no regulations on their use. A spokesperson for the FRA, which is the main regulatory authority for the railroad industry, confirmed in an email to FreightWaves that the agency has never promulgated regulations for the use of wayside hot-box detectors. 


Some, like Christopher Hand, director of research at the Brotherhood of Railroad Signalmen (BRS), think that should change. “We need to have some kind of rules from the government to regulate these hot-box detectors,” Hand told FreightWaves last month.

The AAR announced on Wednesday that all Class I railroads, which comprise the largest rail companies, have agreed to place a hot-bearing detector on average every 15 miles on their tracks. That would amount to a cost to industry in excess of $150 million, according to an AAR spokesperson. 

FreightWaves asked the Class I freight railroads in the U.S. and Canada about their use of wayside bearing detectors. Kansas City Southern, CSX, and BNSF did not respond. 

Canadian railroads CN and Canadian Pacific declined to answer questions on its use of hot-box detectors, deferring to the AAR. Union Pacific stated it has hot-box detectors on average every 19 miles of track. The rail carrier deploys sensors like acoustic bearing detectors, though did not specify how many.

Norfolk Southern said on average it has hot-box detectors every 13.9 miles of track. It currently has five acoustic bearing detectors and has pledged to deploy an additional 13. The NTSB announced Tuesday that it would investigate Norfolk Southern’s “safety culture” in the wake of several significant accidents. 

That the rail industry voluntarily would implement these costly safety systems may be surprising. But, as Zarembski told FreightWaves, the industry has economic reasons to avoid derailments.

“I promise you the railroads don’t like derailments,” Zarembski said. “They’re not good for business. They shut down the track. They can’t run trains when they have a derailment. It’s a big mess.”

Train derailments, while historically low, increased in 2022 compared to 2021

From 2000 to 2022, the Class I railroads’ derailment rate decreased by 31%, according to the AAR

But derailments were up 5% compared to the year prior. (The overall accident rate is at an all-time low.)

Rail workers and the unions that represent them, along with U.S. lawmakers on both sides of the aisle, say one potential contributor to decreasing safety on the railroads is the decline in headcounts and focus on profitability

At Norfolk Southern, for example, FreightWaves reported last month that the rail giant eliminated a key maintenance role that oversees detectors like hot-box detectors in the region including East Palestine. 

“Once they eliminated that position, it fell to the signal maintainers who had no knowledge, no training or very, very little training on these hot-box detectors,” Hand of the BRS said.

It’s not exclusive to Norfolk Southern nor signalmen. Rail crews have massively declined over the past decade. 

Rail employment has sharply declined over the past decade. In the past year, rail carriers have added staff. (Chart: FreightWaves SONAR) To request a SONAR demo, click here.

Many U.S. rail carriers began adopting a set of cost-cutting measures called precision scheduled railroading (PSR) in the 2010s. Critics say PSR has left railroads with shoestring rail crews and equipment. Carriers say PSR has become necessary to keep the industry humming even as rail traffic (particularly coal) falls. 

New legislation seeks to curb future train derailments

A Senate bill introduced on March 1 echoes that sentiment. This bipartisan legislation, if passed, would require detectors every 10 miles of rail track

The Safe Freight Act of 2023, as it’s called, would also set performance standards, maintenance records requirements, temperature ranges that trigger warnings to crew, and repair requirements.

It would be a big change from today’s lack of regulation on such detectors. 

Allan Rutter, who served as the administrator of the FRA from 2001 to 2004, said regulations promulgated by the FRA itself typically involve extensive feedback from industry stakeholders. The FRA also usually conducts a cost-benefit analysis that reveals how much rail carriers should expect to spend (or save) as a result of the regulation. 

However, if Congress votes the Safe Freight Act in, that extensive feedback and research likely won’t take place, said Rutter, now a division head at the Texas A&M Transportation Institute. This sort of legislative movement isn’t unprecedented. Following the 2008 collision outside of Los Angeles between a Union Pacific train and a commuter rail line, in which 25 people died and 135 were injured, Congress enacted a law requiring major rail companies to implement positive train control. This is a set of autonomous systems that prevent train collisions, derailments and other accidents. 

Rutter said shippers, carriers, regulators and other stakeholders should play a role in reducing derailments. (Notably, rail customers, rather than the carriers themselves, own the vast majority of rail cars.)

“Everybody at the table has a job to do to make sure that they look for what it would take to bend the curve downward again, in terms of frequency and consequence on these events,” Rutter said.

What do you think about new regulations on rail? Email [email protected] with your thoughts. And don’t forget to subscribe to MODES for more.

Rachel Premack

Rachel Premack is the editorial director at FreightWaves. She writes the newsletter MODES. Her reporting on the logistics industry has been featured in the New York Times, the Wall Street Journal, Bloomberg, Vox, and additional digital and print media. She's also spoken about her work on PBS Newshour, ABC News, NBC News, NPR, and other major outlets. If you’d like to get in touch with Rachel, please email her at [email protected] or [email protected].