Badly Backed Up: The 1972 Chicago (USA) Train Collision

Max S
13 min readOct 22, 2023

Background

Chicago is a city of 2.75 Million people (as of 2020) in the north of the United States of America, located in the federal state of Illinois 135km/84mi south of Milwaukee, Wisconsin and 45km/28mi east of Naperville, Illinois (both measurements in linear distance).

The location of Chicago in North America.

Chicago is crisscrossed by a network of commuter rail lines, including the Metra Electric Line (alternatively called the Metra Electric District), a
50.7km/31.5mi electrified single- to quad-tracked main line running along 49 stations (as of 2023) between the city’s southern suburbs and the downtown area. Train services on the line were operated by the Illinois Central Gulf Railroad at the time of the accident, which had been formed the same year by merging two previously independent railway companies.

The site of the accident as seen in 2002, the trains approached from the south (bottom of the image). Note that the surroundings changed between the accident happening and this aerial photo being taken.

The Trains involved

Two types of trains operated on the line at the time of the accident, and both types are involved in the accident. One of the two trains was train number 720, a six-car express train service heading northbound on the line. The train was made up of the older, single-level “IC Electric” train cars, a two-car electric multiple unit (EMU) introduced in 1926 when the line was electrified by the installation of an overhead catenary. The IC Electric trains looked much like standard “Pullmann”-type passenger cars from the era, except for having a pantograph on the roof to connect to the overhead catenary, and seemingly missing the locomotive you’d expect in front of a row of Pullman cars. Each car measured 22m/72ft in length at a weight of 64.4 metric tons (motor car) or 40.2 metric tons (trailer car) respectively, and could seat 84 passengers for a total capacity of 168 passengers per unit.

A two-car IC Electric EMU very similar to the one involved in the accident, photographed in 1967.

Running ahead of train 720 was train number 416, a commuter rail service travelling in the same direction. Train 416 was a brand new four-car “Highliner”-train. The Highliner was a two-car bilevel EMU introduced in 1971. The Highliners were modern steel-bodied trains, featuring a more lightweight construction than the heavy IC Electric they were meant to replace, while also having a higher capacity on a train of the same length due to their bilevel design with seating on two levels. They were constructed in “married pairs” of two cars each, which could be linked together into longer trains depending on the required capacity. Each two-car pair measures 51.82m/170ft in length at an empty weight of 122 metric tons and could seat 156 people. Their lighter weight gave them a stronger acceleration and a higher top speed, now reaching 130kph/80mph.

A first-generation Highliner-train, identical with the one involved in the accident, as pictured in the report. The sides were a grayish silver while the end walls were painted black.

The Accident

The 30th of October 1972 showed a gray and cloudy morning as commuter train service #416 approaches 27th Street Station near the Michael Reese Hospital. The train is unusually crowded especially in the rear and leading cars, carrying passengers who had been unable to transfer to another train at a prior stop when said train failed to show up on time.

The driver misjudges his speed on approach to the platform and overshoots it, passing the station at approximately 56kph/35mph and ending up with its rear car ending 183m/600ft past the end of the platform. He consults the conductor on the train, who gives him permission to reverse the train into the station. The line has an automatic signaling system which detects train positions by logging passed signals, he likely figures that their train has passed the entrance-signal to the station and should thus be protected from following trains by a red signal. Guidelines dictate that a reversing train has to be secured by the conductor standing a certain distance ahead of the train’s (then leading) rear end with a flag to warn following trains. The two men decide to skip the so-called flag protection procedure, aiming to quickly get back to the platform to limit the delay the driver’s mistake caused already.

The train begins moving backwards at 7:36am, backing up at around 16kph/10mph while the conductor and driver lean out one side of the train each, keeping contact via the onboard intercom. The driver eventually has to pull his head inside the train due to an overtaking train approaching on the adjacent track, just before his train reaches the platform at 7:38am. The conductor dutifully informs the driver that the back of the train had reached the platform and orders him to slow the train down to a standstill. Moments later #720 slams into the back of the near-stationary Highliner at 71kph/44mph. The train tears through the Highliner’s rear wall as it mounts the frame, shaving off its own leading wheelset, and proceeds to “telescope” through most of the Highlander’s rear car while slowly moving out of alignment to the right, ripping away the car’s right hand wall before coming to a rest on the adjacent track, itself suffering severe damage to its forward 3m/10ft. 45 people are killed in the devastating crash, with a staggering 332 being injured.

The rear of the Highliner-train after train #720 was removed.

Aftermath

The accident had happened right outside two large hospitals, the Michael Reese Hospital adjacent to the rail line and the nearby Mercy Hospital, which provided a fast and large-scale response by medical personnel. This fast and extensive aid provided to survivors along with the incredibly short transport distances to the hospitals is credited with keeping the death toll from growing significantly higher.

The NTSB (National Transportation Safety Board, the agency in charge of investigating transportation accidents in the USA) dispatched investigators to the site soon after the accident occured. They closely examined the remains of the two trains, and also interviewed the Highliner’s conductor, who had survived the accident by jumping off the train right before impact. They found that, while 27th Street Station was an irregular flag stop, meaning trains only stopped if passengers onboard or people on the platform demanded it, train #416 would still have a scheduled stop there every morning as they just about always carried workers heading to the adjacent Michael Reese Hospital. With that, #416 was actually the only train intended to stop at the station between 7:30 and 8:00am, while 17 other trains passed through without stopping.

A fleet of ambulances, police cars, firetrucks and a helicopter surround the jammed-together trains shortly after the accident.

The conductor told the investigation that the train had overrun the station, which in itself was a common occurrence, but usually trains overran by the approximate length of a train car or two, having the end of the train stop several feet past the platform was highly unusual. There was even a buzzer in the cab of the Highliner trains which drivers could sound as a standardized signal to the conductor that they had overrun the station. During a hearing held by the NTSB none of the workers present managed to remember a prior case of a train overrunning a station by as much as #416 had. Usually the conductor would have passengers from the forward cars who wished to disembark walk down the length of the train to one of the doors still at the platform, or a train would just proceed to the next station and have passengers use the opposing service to get back to the station the train overran. Backing a train up was one of the official options, but certainly not the common one. Then again, overrunning the platform by 600ft wasn’t the common way to, well, overrun a platform either.

When asked about the flag protection and why he failed to perform it the conductor pointed out the official guideline 99, which stated:

“Within interlocking, Automatic Block System or Centralized Traffic Control System limits, flag protection is not required against following movements on same track.”

The term “block system” refers to the signaling system in use at the time, which splits a rail line into several blocks, each reaching from one main signal to the next. Only one train can occupy one block at any time, with signals switching (also referred to as “falling”, a term from the era when signals had physically moving sections) to red and thus keeping following trains from entering the same block section.

Firefighters struggle to gain access to the mangled train cars.

The conductor explained that, as the train ran unter an automatic block system, he was not required to perform the flag protection as the train reversed. A factor he missed, which guideline 99 also failed to address, was the distance the train had gone past the station. The Highliner, as the investigators soon found out, hadn’t just overshot the station, it had passed the next signal and thus departed the block section in which the platform was located. This meant the signaling system registered the train as past the station, setting the following section to “occupied” and, rightfully, allowing a following train to enter the station. Once the train started reversing it re-entered the station block, but passing a signal in reverse did not register as occupying a different block section. As such, train #720 was allowed to enter the station, only for the driver to be met by the sight of another train right in his path, reversing.

This, however, led to another question: Why didn’t the driver of #720 stop when he spotted the massive obstacle in his path? Investigators calculated that, at the 48kph/30mph speed limit, the Highliner should have been visible to the driver of the following train early enough to bring his train to a save stop, especially with an emergency stop. The IC Electric wasn’t fitted with a speedometer, with drivers being meant to be able to tell their speed from how fast the surroundings pass by, so the speed on impact was calculated by examining the deformation of the metal caused by the impact. The driver of the of the overtaking train (the one which made the driver of the Highliner pull his head in) was also consulted to estimate the speed as he was alongside #720 right until the accident occured. The speed calculated by the investigators was then used to retrace the final few hundred feet of #720’s journey, including the point where witnesses saw evidence of an emergency stop being initiated just before impact. Adding the speed lost by the distance covered with fully applied brakes to the calculated impact speed resulted in an estimated approach-speed of between 80kph/50mph and 88kph/55mph.

Firefighters remove windows to access the interior of the Highliner.

But the situation wasn’t as simple as “one train driver backed up wrong and another went too fast”. Even at the speed it was going, twice as fast as it was meant to, the driver of #720 would have been able to spot the Highliner at a distance of over 518m/1700ft. Calculations showed that, at the speed it was likely going, #720 would have been brought to a standstill by an emergency stop after 366m/1200ft. The driver of #720, who had survived the collision by abandoning his position and running back into the passenger area just before impact, even admitted that he had been going too fast. He explained that he had seen a yellow signal, which meant the speed limit was dropped to 48kph/30mph. He appeared to not know that it also meant “expect stop”, referring to the following signal, which is why the lowered speed limit was so important.

The report explains that the accident didn’t have a single cause, but was a combination of so many different causes and issues that it can be seen as the result of a complete and catastrophic system failure. It started with the Highliner overrunning a station by a significant distance, and in the process departing the station’s signal block. This moved the Highliner one block further down the line from #720, turning what would have been a red signal yellow (“slow, expect stop, train ahead”). The conductor then decided to back the train up rather than proceed to the next station, despite having left the signal block (likely being unaware of the consequences of how far the train had gone past the platform). He did this despite knowing trains ran at a 2 to 3 minute interval, meaning the following train was already close if nothing went wrong. Poor wording of guidelines had allowed the practice of flag protection to fall out of use, leading to the Highliner backing up without the conductor performing flag protection. While backing up he leaned out the center door of the Highliner’s rear car’s west side and used the intercom while backing up, which put him across the aisle from the emergency brake. The car was also crowded, which meant that there were likley passengers standing between him and the emergency brake, too.

Medical workers who ran over from the adjacent hospital stand among responders at the mangled wreckage.

The close interval meant that trains usually ran under yellow signals, rarely seeing a green signal, which is assumed to have played a role in the driver of #720 not fully complying with the message communicated by a yellow signal. A yellow signal warns of a red signal/train ahead, but due to the close proximity of trains the signals passed by the trains are almost always yellow. And a warning one gets countless times per day for weeks, months or years somewhat loses its power over time. Going by distances alone the driver could have seen the red signal at the end of the platform, which was part of a very short signal block, before he lost the distance required to stop in an emergency, but a pedestrian bridge at 27th Street Station concealed it from view until an approaching train was just about to pass it.

The Highliner’s grayish silver cars had had their end walls painted black, with the lights in the upper corners of the end walls measuring just 3.8cm/1.5in across. This made the train harder to see on a gray, overcast day, as it was unintentionally camouflaged into the surrounding structures, something the two small lights barely broke up. Thus, the driver of #720 might not have immediately noticed what he was looking at when the Highliner came into view, costing decisive seconds before he triggered an emergency stop. At 88kph/55mph the train covered 24m/78.5ft every second, which quickly ate into the safety-distance required to stop.

Looking through a window-frame into what is left of the Highliner’s rear car’s interior after the accident.

The official report dissects the accident down to no less than 18 causing and worsening factors. The causing factors were what led to the accident happening, while the worsening factors were what made the crash be as catastrophic as it ended up being. The report explains that telescoping (one rail vehicle travelling lengthwise through another) was enabled by incompatible structural components, which allowed the rear train to mount the frame of the Highliner. Neither train had cars within it climb each other’s frames, but the Highliner’s structural construction failed to prevent the IC Electric from mounting its frame on impact. Federal Regulations actually demanded structures integrated into the body of new trains that prevent climbing onto the opponent’s frame in an accident, something so-called collision posts were meant to fulfill on the Highliner.

Collision posts were square, reinforced steel pillars standing vertically at the end of each Highliner-pair, framing the aisle and being meant to keep a colliding train from continuing over the frame of the Highliner. However, during the accident #720 hadn’t had any issue mowing down these posts as it began to move through the Highliner-car. The investigation found that the posts hadn’t been properly attached, with the weld attaching the post to the underframe being only 25% complete. Plug welds which attached a reinforcement plate to the lower part of the posts were also found to be incomplete, which further weakened the posts.

A schematic from the report, showing the construction of the collision posts which failed to protect the train car’s interior from penetration due to faulty installation.

The IC Electric had been manufactured before any such regulations were in place, meaning it wasn’t required to have any structures to prevent climbing/telescoping in an accident. This, along with their heavier construction, made the train even more able to mount the frame and move through the Highliner.

The official report closes by declaring late braking by the driver of the Highliner as the root cause of the accident, but it also explains that from that point onwards various factors caused the situation, in simplified terms, to repeatedly go from bad to worse right up until the severely damaged leading car of #720 came to a rest with it’s rear partially inside the rear car of the Highliner. Five recommendations are made at the end of the report, mostly focussing on improving the training and introducing regular checks to make sure rules are adhered to in day to day operation. The FRA (Federal Railroad Administration) is also advised to examine the options of introducing automated train control systems to better prevent trains from colliding and keep drivers from speeding. In the process, they are also advised to create a system that ensures any train entering service complies with the federal demands, which the weakened collision posts on the Highliner didn’t do. The introduction of crash tests for new train car designs is also recommended.

The recommendations actually do not include ensuring speedometers are present on all trains, as the IC Electric was found to be speeding so excessively that a driver would notice even without a speedometer.

Commuters move past the wreckage the day after the accident.

The IC Electric units were retired from service soon after the accident, advancing the average safety standard of the rolling stock. The livery for the Highliner-trains was also reworked, replacing the black sections with bright orange to increase visibility. The first-generation Highliner trains were finally retired in 2016, 11 years after the “Mark 2” Highliners (actually a completely new design) were introduced into service. Most of the old trains were scrapped, with 24 units remaining at various museums. Michael Reese Hospital closed in 2009 and was subsequently demolished, taking away a main source of travellers for the station which today (2023) holds the title of Chicago’s least-used train station.

A preserved first generation Highliner, sporting the improved high visibility livery, photographed at a museum in 2008. Note the small red lights in the upper corners of the end wall.

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Max S

Train crash reports and analysis, published weekly.