Background
Chicago is a city of 2.75 Million people (as of 2020) in the northeast 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 city’s elevated urban train lines form a rectangular pattern around the city’s central business district, referred to as the Chicago Loop (a nickname shared with the district), in the eastern part of the city. The Loop (this article will use the name to refer to the train lines’ rectangular section, unless stated otherwise) was first constructed in 1897 and has a track length of 2.9km/1.79mi. It consists of a dual-tracked electrified rail line going in a rectangle, with the longer expansion being in the south-to-north direction. It borders on the Lake Street (North), Wabash Avenue (East), Van Buren Street (South) and Wells Street (West) and is used by various commuter rail services which are nowadays distinguished by colors (orange, brown, green, purple and pink). The Loop is home to eight train stations (as of November 2023), down from 12 when it opened. Trains will either enter The Loop, turn all four corners and leave in the direction they entered or turn only two corners and leave on a different trajectory. Further complicating things is the fact that The Loop is used both clockwise and counter-clockwise.
There were only four rail lines using The Loop in 1977, each using it in a different pattern:
- The Ravenswood Line (now the Brown Line) operated counter-clockwise on the outer track.
- The Evanston Express (now the Purple Line) and the Loop Shuttle (discontinued) operated clockwise on the inner track, opposite to the Ravenswood-trains.
- The Lake-Dan Ryan Line (now part of the Green Line) operated in both directions but only used the sides of The Loop along Lake Street and Wabash Avenue.
The Trains Involved
The Ravenswood Line train involved in the accident was a six-car Chicago Transit Authority (CTA) 6000-Series train, running as service number #415 in the operational schedule (the number isn’t usually used by the public). The 6000-Series was an electric commuter train introduced in 1950, usually in two- to three-car sets. Standard 6000-Series cars ran in “married pairs”, with each car having a driver’s cab on one end so that a two-car unit had one on either end. They were also run in three-car trains or, rarely, operated as single cars (despite having no driver controls at the back end), and could be combined into long multi-traction trains if required. Each car measured 14.63m/48ft in length at a weight of 18.9 metric tons and could reach 80kph/50mph. They received power from a third rail running along the tracks, somewhat similar to a slot car track. A two-car 6000-Series could carry 98 seated passengers.
Following behind the Ravenswood-train was a train from the Lake-Dan Ryan Line (referred to from here on as the LDR-train), an eight-car train consisting of both CTA 2000-series and 2200-series rolling stock with a CTA 2000-car leading. The CTA 2000-Series, introduced in 1969, was the successor of the 6000-Series, being a two-car electric commuter train usually running in “married pairs” too. Each car measured 14.63m/48ft in length at a weight of 21.5 metric tons and could carry up to 98 seated passengers per two-car unit at speeds of up to 105kph/65mph, although service saw them limited to 89kph/55mph.
The 2200-Series was the successor to the 2000-Series, sharing many of its characteristics (electric multiple unit, married pairs, seating capacity, even their size and weight) with the 2000-Series. They were slightly faster, with a technical top speed of 110kph/70mph, but had the same service speed limit of 89kph/55mph. They can be distinguished from their predecessors by the unpainted stainless steel exterior.
The Accident
An undefined issue with the electrical equipment had occurred in the early hours of the 4th of February, 1977, forcing the dispatch center to have the Evanston Express run counter-clockwise around The Loop instead of the usual clockwise operation. The change of direction put the trains on the same tracks used by the Ravenswood- and Lake-Dan Ryan trains. The increased traffic density led to Ravenswood trains having to stop ahead of entering a station, waiting for the Evanston Express train in front to depart, and then crawl into the station themselves. The delay caused by this process meant that the Lake-Dan Ryan trains would also have to stop ahead of the stations as the space usually used by them to directly pull into stations was now occupied by the Ravenswood-trains.
The system, as inconvenient as it may be, operated all day without incident, up until a Ravenswood-train stopped outside the State/Lake station at 5:23pm to wait for a Evanston Express ahead to clear the station. This left the six-car 6000-Series train sitting just past the center of the northeastern corner of The Loop, above the intersection of Wabash Avenue and Lake Street. The next LDR-train was just a short distance behind it, just pulling out of Randolph/Wabash station on The Loop’s eastern side.
The LDR-train caught up to the Ravenswood-train within seconds, navigating a slight right hand curve before entering the left hand corner of The Loop and, as it failed to stop behind it, running into the back of the stopped train while still not being completely out of Randolph/Wabash station. The collision, referred to by surviving passengers as a “quiet thump” occurred at just 16kph/10mph and could be considered the railroad equivalent of a minor fender bender. However, things took a turn for the worse when Mister Martin, the driver of the LDR-train, apparently panicked after the collision and shoved the throttle-lever forwards, applying full power.
The continued propulsion force from the motors pushed against the barely-damaged Ravenswood-train, which sat with its brakes applied after being shoved forwards 7.5m/25ft by the collision but wouldn’t budge any further. The forces “met” at the coupler between the leading two cars, which started to bend as the center of that two-car unit was pushed upwards into an inverted V-shape, a phenomenon referred to as “Jackknifing” that’s more commonly found with trucks and their trailers in road-accidents. Their frames came into contact a few seconds after the collision, preventing a further increase in angle, at which point they tipped over to the right, dropping off the elevated rail line and crashing down onto the road 6.4m/21ft below. The falling train cars pulled cars 3 and 4 along with them, leading to car 3 ending up down on the road on its right hand side while car 4 hung off the elevated rail line, being caught on the edge by its rear wheelset, as did car 2. 11 people died, all of whom were on the LDR-train, with another 268 people being injured.
Aftermath
Damage to the LDR-train, especially the cars which had completely dropped to the road below, was severe, with the frames and bodies of the cars bending on impact with the ground. Several windows also shattered and/or fell from their frames as the metal bent around them. In contrast, the Ravenswood-train had suffered “very minor damage” as official sources put it. Nobody had been struck by the falling train cars either, but a few passengers were ejected during the fall, ending up pinned beneath the train cars. Some of those passengers allegedly survived, spending hours trapped as the responders fought to free them.
The investigation, after being unable to find any defect on either train that would explain the accident, first focused on Mister Martin, the driver of the LDR-train. His medical records were fine, he had been prescribed glasses for reading but wasn’t required to use those while operating a motor vehicle (which includes train driving). His employee records, however, were far from fine. They listed a long string of rule violations, from driving roughly, failing to show up for shift and wearing improper uniforms to reading while driving and false use of emergency brakes. He had also driven past a red signal twice, derailing during one of the two instances. And all of that, one should know, was just from within a year, as union contracts prohibited usage of an employees disciplinary records (where such events are recorded) from more than a year ago for investigations. The CTA had had him take part in several “repeated instruction”-seminars and had also escalated to temporary suspensions for repeated and/or larger rule violations.
Things went from bad to worse for Mister Martin when police officers retrieved his bag from the wreckage of the train, finding four self-made cigarettes containing marijuana inside. Obviously, illegal drugs are the kind of thing you don’t want police to find in your belongings after you crashed a train.
Mister Martin voluntarily provided urine and blood samples for examination, with the blood testing negative for alcohol, amphetamine and barbiturates (a chemical found in sedatives). However, one of the two laboratories who received the urine samples reported finding delta-9-Tetrahydrocannabinol-acid, with the second laboratory finding none, retesting after recalibrating their equipment, and then reporting the same finding. The acid is present in urine after a person ingested delta-9-Tetrahydrocannabinol (THC), the active “high-causing” substance in marijuana. However, neither laboratory could pin down how much time had passed between Mister Martin consuming the drug and the accident occurring.
But even with the driver under the influence of drugs to some degree there still should have been systems in place to keep trains from running into each other, even under unusual conditions as those on the day of the accident, when trains had to “stack up” outside stations and wait for the train in front to proceed along the route.
Chicago’s elevated rail lines operate with two cooperating signaling systems, referred to as Automatic Train Control (ATC), one of which being trackside signals as part of a block section system. Traditional block sections are predetermined stretches of the rail line which only one train may occupy at a time. The sections begin and end at a signal installed next to, or in some cases above the track. This is why they are often referred to as “signal blocks”. Each signal block on The Loop contained 91.44m/300ft of track, and the guidelines dictated that an empty block was to be between two occupied blocks to ensure sufficient stopping-distances. This means if a train’s leading end was at the “0 feet mark” the next train wasn’t meant to be anywhere closer to it than the 600ft mark (183m).
The trains operating on the elevated rail lines are also fitted with in-cab signalling, a row of three colored lights (red, yellow and green) not too different in appearance from a small traffic light. Furthermore, the trains had two yellow lights built into the speedometer, which could mark 24kph/15mph and 56kph/35mph respectively. The green light of the in-cab signalling system wasn’t used on The Loop due to the density of even regular operations, the rest of the components were used to communicate the following information:
- Yellow cab signal permanently on, 56kph/35mph indicator illuminated: Two blocks ahead are empty.
- Yellow cab signal permanently on, 24kph/15mph indicator illuminated: The block ahead is empty, the one beyond is occupied. Alternatively, this could refer to a special restriction (such as a construction site).
- Red cab signal permanently on, no indicator illuminated: Block ahead occupied. Stop.
- Red cab signal flashes, 24kph/15mph indicator flashes: Block ahead likely occupied. Stop. Train may proceed after stopping if it does so at no more than 24kph/15mph while maintaining the ability to stop within sight.
The permanently illuminated red cab signal would also switch to flashing when the train is decelerated to 5kph/3mph or less. At that point it would allow the train to stay in motion, but at no more than 24kph/15mph. In other cases, running a red signal or breaching the indicated speed limit would trigger an automatic stop.
The trains had no data-loggers the way you might find today, so the investigation was left to try and reenact the minutes leading up to the collision. They knew where the Ravenswood-train had stood, and when the LDR-train had previously stopped, so they went and backtracked its path from there. They found that the most likely chain of events began when Mister Martin approached the Randolph/Wabash station, receiving a red signal in his cab due to the Ravenswood train just a few hundred feet up the line. Mister Martin insisted that he didn’t see the train ahead from the point when he was stopped at the platform onward, which the investigation doubted due to the close proximity putting the two trains easily within visual distance during the reenactment.
Stopping at the platform registered as “instruction obeyed” with the signaling system, switching it to a flashing red and turning on the 24kph/15mph indicator on the speedometer. He then pulled away from the platform at low speed, staying below the speed limit which is why the automatic emergency stop wasn’t triggered. It was never determined why he departed with the stopped Ravenswood-train within sight, with some sources pointing to records and witness statements from other days were Mister Martin was caught chatting with passengers while driving (the driver’s cabs weren’t walled off from the passenger area). It’s possible that he was doing that, taking his attention away from the traffic up ahead. Another theory proposes that the “didn’t see it” was a flat lie, and that he had simply expected that it would move up the queue before he got to the curve. The distraction-theory is more common, and, given the events that unfolded, arguably puts Mister Martin in a less unfavorable light.
Since the Ravenswood-train up ahead couldn’t move out of his way his train struck the stopped train at low speed, with some surviving passengers making statements along the lines of “we felt a bump and stopped, I thought we would move along in just a moment”. It’s been argued that the bump from the low-speed collision made Mister Martin fall forward, pushing the throttle lever forward as his hand was resting on it. The alternative explanation is that he panicked and shoved the throttle lever forwards after the collision. This, too, could never be determined with 100% certainty, but either way the fact remains that Mister Martin performed a (as far as the investigation could tell) inadvertent application of full throttle, rather than shutting the train off and assisting the conductor in evacuating the train.
Once full throttle was applied the situation quickly escalated out of Mister Martin’s hands, with the forward cars, standing on curved track, being the weakest link as the LDR-train pushed against the stopped train in front. Thus, the leading two cars lifted off the tracks at their shared coupler and, when they couldn’t rise up any further, fell over, out of the curve and with that off the bridge. Had the very same collision occurred a few feet back, on a completely straight track, the train might have still “buckled” at some location, but would’ve been less likely to fall over, let alone off the bridge.
Mister Martin was fired from his job six months after the derailment, three months before the official investigation concluded and blamed him. There seems to be no public record of criminal proceedings against him, so it’s unclear if he was put on trial, and if he was what the outcome was.
The CTA changed the rules surrounding the in-cab signalling after the accident, with the new “Rule 6.4” dictating that a driver now had to stop and contact the traffic controller when they received a flashing red light, who would then decide if the train could proceed. The flashing red had been originally introduced to combat false “occupied”-reports from the block system, which is why trains were allowed to proceed with it but not with a permanent red. A new light, labelled “R6.4”, was also installed in the driver’s cabs to remind drivers of the new rule.
The leading four cars from the LDR-train were scrapped after the accident, each suffering damage that easily totaled it. The rest of the train cars involved were repaired and returned to service, until their types were retired from service between 1992 (6000-Series) and 2014 (refurbished units from the 2200-Series).
The accident is not only the worst accident to occur on Chicago’s elevated train system to this day (November 2023), but also has two characteristics that make it special. For one, the devastating part of it happened after the collision itself had occurred and all trains involved had come to a stop. Secondly, the complex signalling system in use had been seen as a way to guarantee safety from such accidents, but had been working as intended throughout the event-sequence without managing to avoid it. The fact that such a severe accident could still occur emphasized that proper and thorough training as well as adherence to the rules taught are not to be underestimated regardless of what parallel systems are in place. With lessons learned from and since this accident a repetition of it is as close to impossible as it could reasonably be.
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