Anatomy of a Tank Car

Editor’s Note: I have discovered a Spotify playlist called “Songs About Trains” which I recommend you listen to while reading this article. Also, Part I of this series is here.


In the second part of this brief series on rail safety, we’re going to talk about rail tank cars, specifically, the tank cars known as  DOT-111As in the United States, CTC-111As in Canada or, more generically, Class 111A cars.

But first, I want to take a step back and give this discussion some context. Last week, I noted that the 2013 Lac-Mégantic rail disaster was the worst in a string of rail accidents that had occurred across North America around that time, but what I didn’t explain was that this string of accidents coincided with an extraordinary increase in the shipment of crude oil by rail, largely as a result of the shale oil boom in the United States.

Photo of a frack job in progress in the Bakken Formation in North Dakota.

Fracking the Bakken Formation in North Dakota, 2011. (Photo by Joshua Doubek, CC BY-SA 3.0, via Wikimedia Commons)

Crude shipments by rail in the US went from 9,500 cars in 2009 to 400,000 cars in 2013. Here in Canada, they increased from about 6,000 cars in 2009 to an estimated 14,000 cars in 2013, according to Statistics Canada and the Canadian Association of Petroleum Producers. (In Canada, this was due to both US shale oil and Alberta Oil Sands bitumen.)

Writing in the Chicago Booth Review in 2018, Brian Walheimer said rail transportation of crude in the US peaked at almost 1 million barrels a day between 2010 and 2014 and this 2017 paper for the US National Bureau of Economic Research (NBER) says that in 2014, roughly half the crude shipped out of North Dakota (the third-largest oil producer in the US, after Texas and the Gulf Coast region) went by train and half by pipeline.

The NBER paper argues that rather than worrying about oil spills and accidents related to oil transportation, we should be looking at air pollution and GHG emissions, which are more costly than spills and accidents and which are much higher for rail than for pipelines. The paper concludes that we need to build more pipelines, which seems to me to be accounting for “externalties” very selectively; if you were truly concerned about air pollution and GHG emissions, you would hardly be advocating the continued use of oil, no matter how it was transported.

But the NBER paper also fails to come to grips with a constraint on pipeline construction in the Bakken fields, which Walheimer explains this way:

…as pipeline developers sought long-term contracts from oil shippers, a curious thing happened. The availability of rail as a transport option reduced demand for pipeline capacity, find Chicago Booth’s Thomas Covert and University of Chicago Harris School of Public Policy’s Ryan Kellogg, even though shipping by rail costs more and causes more environmental damage. They argue that “crude-by-rail may be an attractive transportation option in spite of its higher costs.”

Covert and Kellogg argue this is because:

…rail infrastructure already exists between the upper Midwest and nearly every major refining center in the country, crude-by-rail allows shippers the flexibility to decide when and where to ship crude” on the basis of changes in prices…

Their research suggests that rail’s flexibility reduced demand for pipeline capacity.

A photo of a train pulling tank cars filled with crude oil.

A westbound Norfolk Southern Railway freight train near Altoona, Pennsylvania, 10 May 2016. The Deep Rock Refining Company tank cars, marked DPRX, were built in the 2010s to transport crude oil. (Photo by James St. John, CC BY 2.0, via Wikimedia Commons)

Keith Stewart, a climate and energy campaigner with Greenpeace, made a related point to the CBC back in 2013, explaining why producers from the Bakken area were so heavily dependent on rail transportation:

Unlike oil sands developments, which are expected to produce for several decades, oil wells in the Bakken formation only produce for about 10 to 12 years, so it is not always economical or easy to connect them to the existing oil pipeline in the U.S., says Stewart.

Building costly pipeline infrastructure is simply not worth it for the companies developing these wells.

“The shale oil wells are rapidly moving in a physical sense, so building a pipeline that would take 50 years to pay for itself is not economically viable,” says Stewart. “With rail, you can extend the network of tracks relatively easily and service multiple wells in a certain area.”

Basically, as long as we’re dependent on oil, oil is likely to be shipped by rail. But it’s also worth remembering (although it’s probably pretty fresh in everyone’s minds after the East Palestine derailment) that crude is not the only hazardous material shipped by rail.

All of which is a long-winded way of explaining why I’m going to talk about tank cars this week.


Raising alarms

In 2013, at the time of the Lac-Mégantic explosion, DOT 111A cars accounted for “up to 80% of the Canadian fleet and 69% of U.S. rail tank cars” and they were, unsurprisingly, involved in many of the accidents from that period.

But regulators in Canada had been sounding the alarm about issues with these tanker cars for over 20 years prior to Lac-Mégantic, as had US regulators. In a rail accident report on an incident involving Class 111A cars in Lethbridge, Alberta in 1994, the authors noted that:

…steps were taken in the United States in 1986 to preclude certain hazardous materials with high inhalation toxicity and/or high volatility from being carried in Class 111A tank cars. In Canada, the new standard (CAN/CGSB-43.147-94) is a similar positive step towards reducing these risks. However, many toxic and volatile liquids are still permitted to be carried in Class 111A tank cars in Canada and from the United States to Canadian destinations.

A diagram of a DOT 111 tank car

Illustration by Chris Philpot (Source: Mother Jones)

The TSB recommended that:

The Department of Transport take immediate action to further reduce the potential for the accidental release of the most toxic and volatile dangerous goods transported in Class 111A tank cars—for example, require design changes to improve tank car integrity in crashes or further restrict the products that can be carried in them.

I’m going to quote that Lethbridge report as well as two other reports at greater length to give you an idea of the type of incidents that were occurring long before the boom in rail shipments of crude oil.


Lethbridge, Alberta 1994

A Canadian Pacific Limited (CP) freight train traveling westward derailed due to a rail fracture (the result of “undetected fatigue cracks in a rail that had worn beyond condemnable limits”). Six tank cars containing methanol derailed. Four of the derailed cars “lost product” resulting in the release of approximately 230,700 liters of methanol and the evacuation of a 20-square-block area of Lethbridge. The “spilled and remaining” methanol was removed from the site and there were no injuries as a result of the accident but five tank cars were “extensively damaged” and 300 feet of track destroyed.

As noted above, the TSB recommended design changes for the tank cars and a ban on their transporting certain substances.


Gouin, Quebec 1995

A Canadian National (CN) train consisting of three locomotives and 44 cars of sulphuric acid derailed at Mile 82.2 of the La Tuque Subdivision, near Gouin, Quebec. Of the 28 cars that left the rails, 11 leaked 230,000 liters of sulphuric acid into the Petit lac Masketsi and the Tawachiche River. No one was injured but residents were told not to use lake water “until the contamination was neutralized.”

Removing the sulphuric acid from the derailed cars took eight days, and bringing the pH level of the water in the lake back to normal took over three months and approximately 725 tonnes of limestone. The TSB said there had been “no apparent long-term effect on aquatic life.”

The report states that 22 of the derailed cars (all of which were DOT 111As) were extensively damaged (six were scrapped), 2,000 feet of track was destroyed and another 500 “slightly damaged” and a small railway bridge sustained “substantial damage.”

The TSB said the derailment was caused by “gauge loss” that was “likely attributable to deteriorated ties.”

But it also focused on the DOT 111A cars, noting that:

TSB accident data suggest that over 60 per cent of product releases from Class 111A cars were from damaged top fittings; over 25 per cent were due to structural failure of the tank, mainly from punctures in the head or shell; and about 10 per cent were from damaged bottom fittings.

The report says that Transport Canada was involved in “various research and development projects aimed at identifying and classifying critical tank car anomalies” but that, in the  meantime, “Class 111A tank cars carrying dangerous goods remain particularly vulnerable to product release from damaged top fittings in the event of a collision or an upset.”

It then cites the recommendation from its 1994 report on the Lethbridge derailment.


 Lévis, Québec 2004

A CN freight train carrying gasoline and heating oil was traveling from the Ultramar Refinery (now the Valero Jean Gaulin Refinery) in Saint-Romuald, Lévis to Montréal on a line that:

…was built between 1879 and 1884. From 1987 to 1995, annual railway traffic totalled approximately 850 000 tons and included both passenger and freight trains. Following the introduction in 1996 of unit trains carrying hydrocarbons from the Saint-Romuald refinery, traffic has gradually increased to reach approximately 6 million tons annually.

The train, which consisted of 68 loaded tank cars and two locomotives, had traveled 11.2 miles when a “train-initiated emergency brake application” occurred and 18 cars (all DOT 111A) derailed, spilling 200,000 liters of gasoline and diesel oil—all of which was, apparently, recovered—into a “marshy area” beside the track.

Photo of a 2004 train derailment near Levis, PQ

Aerial view of derailment near Levis, Quebec, 2004. (Source: TSB)

Although the accident was basically the result of the track having been constructed on peat, the TSB once again notes that the DOT 111A cars are more susceptible to puncture and more likely to release product when involved in an accident:

The tank shells and heads were breached as a result of the impact when the tanks jackknifed. In addition, the isolation valves and rollover protection systems were ineffective and, as a result, there was a significant spill of hydrocarbons.

The TSB acknowledges that the number of products the cars are allowed to transport has been reduced and that some design improvements have been introduced for new Class 11A tank cars to “provide better protection to valves in the event of a rollover.” However, it writes:

…safety enhancements included in the standards do not apply to Class 111A tank cars with a maximum gross weight of 263 000 pounds or less, or to other non-pressurized tank cars, even though they represent the majority of recently built cars. Furthermore, the project “Next Generation Tank Car” initiated by [Transport Canada] the FRA [the US Federal Railroad Association] and the industry, concerns only the construction standards of high-pressure tank cars used to transport hazardous goods. Therefore, a large number of tank cars carrying dangerous goods are not reinforced and are vulnerable to punctures and will continue to present risks of puncturing, even during derailments at moderate operating speeds.

In 2007, the TSB recommended:

The Department of Transport extend the safety provisions of the construction standards applicable to 286 000-pound cars to all new non-pressurized tank cars carrying dangerous goods.



In 2011, as a “voluntary good faith effort,” the tank car committee of the Association of American Railroads (AAR) published a new standard for tank car construction, known as CPC-1232, to:

… improve the crashworthiness of tank cars shipping petroleum crude oil and denatured alcohol (ethanol). The new standard required thicker steel shells for non-jacketed tanks and normalized (heat treated) tank heads and shells, head protection and top fittings protection. The requirement took effect for all cars ordered after October 1, 2011.

We’ll talk about the effectiveness of the CPC-1232 cars next week, here I just want to note that crude oil was still being carried in classic 111A cars in Lac-Mégantic and six months after Lac-Mégantic, a train that derailed near Plaster Rock, New Brunswick was pulling DOT 111A cars carrying dangerous goods.

A Transport Safety Board of Canada diagram of a 2014 derailment in Plaster Rock, NB

Source: TSB

The train was a CN freight train consisting of 122 cars (66 loaded and 56 empty), three head-end locomotives and one “distributed power” locomotive in the middle. It was on its way from Toronto to Moncton when a broken axle on a hopper car triggered a “train-initiated emergency brake application” that resulted in 19 cars and the distributed power engine derailing and catching fire. As a result of the derailment, about 230,000 liters of hydrocarbons spilled from the tank cars, leading to the evacuation of about 150 residents. About 350 feet of track was destroyed. There were no injuries.

The TSB investigation found that of the derailed cars, 12 were tank cars carrying dangerous goods, including five cars of crude oil and four of butane.

Four of the derailed tank cars were Class 111As, two sustained no damage but two, built in 1996 and 1984, had their heads and shells punctured and “released product and fed the pool fire.”

The derailed CPC-1232 cars had fared better, but did not perform as well as expected.  In fact, in January 2014, the same month as the Plaster Rock accident, the TSB reported that:

…damage to the pre-CPC-1232 tank cars in Lac-Mégantic clearly indicates that product release could have been reduced had the tank car shells and heads been more impact-resistant. Design improvements to these types of cars are needed to mitigate the risks of a dangerous goods release and the consequences witnessed in the Lac-Mégantic accident.

The TSB recommended that:

The Department of Transport and the Pipeline and Hazardous Materials Safety Administration require that all Class 111 tank cars used to transport flammable liquids meet enhanced protection standards that significantly reduce the risk of product loss when these cars are involved in accidents.

In April 2014, Transport Canada agreed to:

…immediately and unilaterally prohibit the use of the highest-risk group of older DOT-111 tanks cars. A Protective Direction under subsection 32(1) of the Transportation of Dangerous Goods Act, 1992 was issued on 23 April 2014 and prohibits the use of tank cars that have no continuous reinforcement of their bottom shell to carry any Class 3 flammable liquids, including crude oil and ethanol. Industry had 30 days to fully comply.

TC will require that all pre-CPC 1232/TP 14877 tank cars used for the transportation of crude oil and ethanol be phased out of service or retrofitted within 3 years.

Which brings us  to the changes in regulations that happened in 2015, which we will take up next week.