Background
Pomponne is a municipality of 4168 people (as of 2020) in northern France, located in the Ile-de-France region 106km/66mi southwest of Reims and 25km/15.5mi east of Paris, the French capital (both measurements in linear distance).
Pomponne lies on the Paris-Est–Strasbourg-Ville railway, a dual-tracked electrified (since 1962) mainline connecting the French capital with Strasbourg on the German border. The line opened in three sections between 1849 and 1852, operated as Line 1 of the Chemins de fer de l’Est (often referred to as just Est Company in English), a private French rail operator. The eastern section of the line changed ownership between France and (what became) Germany several times in the following decades, a back-and-forth still visible today by a crossover at Sarrebourg/Saarburg where the two tracks switch sides as Germany and France didn’t operate in the same traffic-pattern.
The Trains Involved
Service Number 55 was an irregular regional passenger service from Paris to Nancy, which had been added to the schedule in order to deal with the increased traffic ahead of Christmas. Not much is known about the train’s configuration, except for the East Company being forced to include older, wood-bodied passenger cars in the train as the increased traffic saw them running out of passenger cars in general.
Service number 25 was a passenger express service from Paris to Strasbourg, consisting of several express passenger cars pulled by Est 241.017. The Est 241 is a class of French express passenger steam locomotives introduced in 1925 (prototype) and 1930 (mass production) respectively in order to deal with the new, heavier all-steel express passenger cars while also achieving higher speeds. The locomotives are built on a 4–8–2 “mountain”-pattern, meaning they have two leading axles, four driven axles and a single trailing axle carrying the locomotive itself while a pulled four-axle tender carried up to 8.5 metric tons of coal. Each Est 241 measures 26.3m/86ft in length including the tender at a service-ready weight of 195 metric tons. Their power-output of 2574kW/3452hp made them Europe’s strongest steam locomotive at the time of their introduction and gave them a top speed of 120kph/75mph.
The Accident
The 23rd of December 1933 was a nasty winter day in Paris, with blistering cold and heavy fog. The Est Company had entered several irregular trains into the schedule to help with the extremely high passenger volume ahead of Christmas, but these additional trains certainly didn’t help operations as the weather was already wreaking havoc on the schedules.
Service #55 is one of these additional trains, a packed regional service from Paris’ Gare de l'Est (eastern station) to Nancy, 285km/177mi linear distance to the east. The train pulls away from the platform in Paris at 7:22pm, quite a bit behind the scheduled 5:49pm departure. The first part of the journey was uneventful, reaching Vaires-sur-Marne where the line slims down from four to two tracks. A rail bus is sitting in the outside track just beyond the station, waiting to depart eastbound on the now dual-tracked line, and Service #55 has to stop at a red signal to let it go first.
Following behind #55 is the Paris-Strasbourg express, which had been held back at Paris itself with a delay from 6:16pm to 7:29pm. The express had few stops along its journey, and is thus approaching the municipality of Pomponne, where #55 has stopped, at 110kph/68mph in heavy fog. The train has been ordered by the trackside signals to stop at Vaires-sur-Marne due to the stopped regional train up ahead, but fails to do so and speeds through the station at full speed. Disaster is unavoidable, and the heavy express thus slams into the back of the regional train, which had just barely started moving again, just after passing through the station at 8:12pm. The wooden bodies of the regional train’s rear five cars are no obstacle for the heavy express train, being obliterated as the locomotive plows more through than into them. The resistance from the debris and steel frames eventually builds up enough to finally shove the rest of the regional train forwards, allowing both trains to come to a stop rather than letting the express proceed all the way to the regional train’s locomotive. 204 people die in the collision, exclusively aboard the regional train, and another 120 require medical attention for their injuries.
Some sources claim as high as 230 victims and 500 injured, I went with the most commonly claimed numbers.
Aftermath
Passengers in the rearmost cars of the regional train didn’t stand a chance in the accident, with the bodies of the train cars just about ceasing to exist, leaving broken and splintered debris separated from their bent steel frames. Some metal debris landed on the oncoming track, connecting the rails by coincidence which reported the track “occupied” to the signal system, allowing an inbound train to stop just before running into the wreckage as its signals suddenly switched to “stop”.
Police officers who arrived at the site found themselves overwhelmed with the scale of the disaster and proceeded to seize random private cars from local residents, using them to transport the injured to hospitals. Priests and bishops came to the site to bless the dead, who were then taken to Gare de l’Est where a luggage handling hall was repurposed as a makeshift morgue. Some survivors had to wait for hours to be transported, huddling around fires lit by responders with debris from the wooden cars. Some sources claim that a few survivors suffered hypothermia due to the exposure to the winter weather.
The accident was France’ second-worst rail accident of all time and the worst one in peacetime, falling in line behind the 1917 Saint-Michel-de-Maurienne derailment, where the derailment of an overloaded troop transport claimed over 700 lives.
The investigation quickly zeroed in on the actions of the express’ locomotive crew as the cause of the accident, claiming they must have ignored a signal telling them to stop. This theory was rejected by Mister Daubigny, the locomotive’s fireman, who insisted that he had received all clear signals and only realized something was wrong when he saw the red lights marking the back end of the regional train up ahead, at which point there was nothing the crew could do to avoid the disaster. This version of the events was backed up by the driver, Mister Charpentier, but the public prosecutor still ordered the two men to be detained on charges of manslaughter. This decision caused widespread protests driven by the Unions, leading to the men being released after 4 days.
The proceedings saw Mister Charpentier evaluated by an eye-doctor, who diagnosed color-blindness of an undocumented degree/form, which, along with the fact that he wasn’t on the signal-side of the train, led to the charges against him getting dropped. Checking the signals wasn’t his job, and even if he did he wouldn’t have been able to tell what color light was shining at him. Mister Daubigny, however, was put on trial as it was claimed that he disregarded signals and generally failed to slow the train down to a speed appropriate for the foggy conditions.
The investigation also looked into faults with the signaling system, which consisted of two different systems that weren’t really intended to be used alongside each other. Standard light signals were in use from Paris all the way to Vaires station, beyond which physical signals were used instead. These consisted of metal “paddles”, whose position was clarified in low visibility and/or at night by shining a petroleum lamp through tinted glass inserts. The colors we know of railway signals today (green for “clear”, yellow for “slow/expect stop” and red for “stop”) weren’t in use with those signals though. That color-system had only been introduced in 1926 by Mister Verlant, an engineer, being fittingly named the Verlant-Code. The traffic ministry had given railway companies five years to switch to the new system, something the Est Company had yet to follow through with.
Thus, the 4km/2.5mi ahead of Pomponne had not been fitted with a unison signalling system. Three of its signals, numbered 13, 15 and 17, showed “clear” with a white light and “stop” with a green and a red light. The signals in between were simple repeater-signals showing white for “clear” and two green lights for “expect stop”. The prosecution claimed that Mister Daubigny either didn’t pay attention to the signals at all or mistook them for the new color-system (green means clear), possibly aided by his high speed giving him only a brief glance at each signal. Mister Daubigny’s defense argued that the white lights were quite hard to see in the fog, in support of his claim to have received “all clear” signals. An expert contracted to examine the signals after the accident called it highly unlikely that the signals showed the right indication to the regional train, then wrong indications for the express and then went back to the right indications when investigators showed up.
The doctor who had examined Mister Charpentier also examined Mister Daubigny, attesting him an above-average sharpness of sight. This meant he would have been able to identify signals earlier than the average fireman. His records also didn’t show a single instance of disregarding a stop-order throughout a lengthy career. Lastly, there was a documented failure of signal 15 five weeks after the accident, while the investigation was ongoing, where it showed the wrong indication.
Another factor in the investigation were the “crocodiles”, wavy steel beams mounted in the center of the tracks. These touched up against metal brushes mounted underneath the locomotives, closing a circuit and transmitting one of two messages depending on the setting of the signal they were mounted next to. A closed signal will send a 20V current to the crocodile, which is transmitted to the locomotive, triggering a whistle which the driver or fireman have to reset. Both the whistle and its reset are logged on the locomotive’s “Flaman-stripe” data-recorder. A failure of the electrical system would automatically attach explosive capsules to the track, which give a loud boom when detonating under the train’s wheels. This would communicate an absolute stop order.
An examination of the express locomotive’s data recorder showed that no signal-data had been recorded at all, and the locomotive crew claimed that they hadn’t heard a whistle in the cab, much less reset one. Survivors reported hearing a bang that could stem from the explosive capsules, but not when the locomotive passed the signals but significantly later, when the bistro car did. This indicated that the system, if it switched to “stop-mode” at all, did so well after it should have, and since it was directly linked to the signal the signal may have really shown a “clear” indication when the locomotive passed it.
The investigation found that ice could have formed from fog and condensation on the relays and/or the mechanical linkage of the signal and crocodiles, which limited their ability to transfer power/move. This was usually combated by having workers head out in sub-zero temperature nights (such as the one ahead of the accident) and apply oil to the components in question, but the leading engineer of Est Company admitted during the investigation that the company had decided to experiment with ceasing the practice of oiling the componentry. He went on to explain that the conditions experienced during the night ahead of the accident could have led to approximately 3 millimeters of ice buildup, which “would’ve essentially isolated the relays”. In summary, the theory in support of Mister Daubigny’s claim said that the signal’s internals had been frozen over from fog due to insufficient lubrication and protection, meaning they showed “clear” despite the signal box setting them to “stop”. Mister Daubigny thus didn’t slow the train down, assuming the path ahead was clear. The fact that the train ahead was an irregular service also meant that he may not have had a routine of stopping in that location. The vibrations from the passing train then “unstuck” the signal internals, setting the detonator caps and causing them to detonate when run over by the bistro car, some way down the train and likely too far back for the locomotive crew to hear over the roar of the steam locomotive.
Mister Daubigny was put on trial for manslaughter in late December 1934, almost to the day a year past the accident. Engineers and experts from the Est Company insisted that the signals had been fine and Mister Daubigny had simply failed to obey them, while other technicians supported the theory of a signal failure, aided by firemen telling of earlier signal failures they had witnessed. The public prosecutor eventually admitted that there were “doubts” in the story and pleaded for a charge of manslaughter under lessening circumstances, but the judge argued that “two fully separate, contradictory theories” were no basis for a conviction and advised the jury to find the defendant not guilty. The sentence was eventually handed down on the 24th of January 1935, finding Mister Daubigny cleared of all charges as “any reasonable doubt has to be used in favor of the defendant”.
The French signaling-system was urgently unified and overhauled after the accident, including a switch to exclusive use of the new Verlant-code. The mainline pre-signal switched from two green lights to a yellow one, “stop” was now a singular red light instead of red and green, “clear” changed from white to green to make it easily distinguishable from other lights. Lastly, combination signals that serve as both main- and pre-signals were redesigned to make them easier to read, and the illumination of any signal was changed from petroleum lamps to electric light bulbs, giving a brighter and thus better identifiable light. The French government also decided to have railway companies phase out wood-bodied passenger cars, although this process wouldn’t finish until 1962 due to serious delays caused by the second world war starting just 4 years after the trial ended. A modernized version of the crocodile-system is still in use in Belgium, the Netherlands and France today, but is being phased out in favor of internationally standardized and more capable systems.
The Est 241 steam engine, by that time renumbered as series 241 under the newly founded SNCF (French national railway) saw its last unit withdrawn from service in 1965 after spending its last years as a backup for new diesel locomotives. The prototype is preserved as a stationary exhibit in the railway museum of Mulhouse (France) while the second survivor, Est 241.001, was restored in the mid-1990s and is now in the hands of an enthusiast club. It’s used for historic train tours in Germany and Switzerland as the last working unit of its type, also making it Europe’s second-largest operational steam engine. It’s currently (December 2023) in the last stages of a five-year overhaul.
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