Gaslit: The 1924 Bellinzona (Switzerland) Train Collision

Bellinzona is a city of 43360 people (as of December 2020) in southern Switzerland, located in the Canon of Ticino (“Tessin”) 23km/14mi north of Lugano and 70km/43.5mi southwest of St. Moritz (both measurements in linear distance).

Bellinzona lies on the Gotthard Railway, a 206km/128mi double-tracked electrified main line connecting the southern tip of Switzerland with Immensee near Lucerno. Opening on the first of January 1882 the line crosses the Saint-Gotthard Massif at a height of up to 1151m/3776ft above sea level, making it the second highest railway line in Switzerland. Being part of an important international corridor the line was electrified in 1922. From the beginning the line was used for everything from regional passenger services to long distance international freight and express trains. Due to the strong incline of up to 28‰/2.8% trains commonly use more than one locomotive to make it up the mountain.

The site of the accident seen from above today. Train #70 came from the north (top of the image), #51B from the south (bottom of the image).

Night Express Number 51 was an overnight express passenger service from Milan to Basel, which consisted of a Swiss and an Italian part which were usually joined together once the Italian cars reached Switzerland. Due to the Italian train carrying a 46 minute delay the train was to pass through Bellinzona in two parts, with the Italian cars running as train #51b as they approached the Gotthard. Pulling the train was a pair of SBB (Swiss national railway) Be 4/6, a six-axle electric express train locomotive introduced in 1920 specifically for the Gotthard Railway. Each Be 4/6 measures 16.5m/54ft in length at a weight of 110 metric tons. They could reach a top speed of 75kph/47mph. The second locomotive on the train, number 12342, had just been delivered a year prior to the accident.

An SBB Be 4/6 identical to those involved in the accident, photographed in 1925.

Following the two locomotives was a heater car (a freight car with a boiler to heat the steam-based heating-system aboard passenger cars) followed by a four-axle type AB4ü passenger car from the Baden State Railway and a row of seven four-axle passenger cars. The AB4ü-car was an older wooden design with gas-powered lighting fixtures fed from two underfloor tanks with 1.2m³/42.4ft³. Due to the Easter holiday the train was very well booked, the customs-check at the Italian-Swiss Border had shown a near-full train which included 52 Italians, 45 Germans, 15 Swiss nationals, 4 US-Americans and 2 people each from Norway, France, the Czech Republic and the UK.

A model of a AB4ü passenger car similar to the one involved in the accident. The gas tank is clearly visible.

Travelling in the opposite direction was Train number 70, an express service from Arth-Goldau to Milan. It consisted of an SBB Be 4/6, a heater car and a luggage car followed by several modern express cars with a heavy steel construction. To manage the steep mountain railway the train had received an SBB Be 4/7 as a helper-locomotive, driven by a train driver who usually only worked in shunting-operations but had been assigned the train due to the high demand around Easter. The SBB Be 4/7 had been introduced in 1921 as a competitor of sorts for the Be 4/6, being similarly meant for the Gotthard Railway but featuring direct axle-motors instead of the coupling rod design of the Be 4/6. Each Be 4/6 measures 16.24m/53.3ft in length at a weight of 111 metric tons and can reach 75kph/47mph.

An SBB Be 4/7 identical to the one pulling train #70 at the time of the accident.

Running ahead of train #70 was freight service number 8572, a freight train of unknown configuration, which had accumulated a delay of 55 minutes as it descended the Gotthard Pass. It was scheduled to let the express train to Milan pass at Bellinzona station, as the passenger train could travel faster than the freight service.

On the 23rd of April 1924 at approximately 2:10am the dispatcher at Ambri-Piotta station decides to have express train #70 overtake the slower freight train at his station instead of waiting for it to reach Bellinzona station 58km/36mi down the line as scheduled. He called every station south of Ambri-Piotta down to Biasca (19km/12mi north of Bellinzona) to notify them of the spontaneous change. Why he chose to not notify Bellinzona’s dispatcher, or why Biasca’s dispatcher didn’t notify his colleague at Bellinzona station is unknown.

At the same time as the dispatcher notified his colleagues of the changed schedule a freight train had reached Bellinzona’s freight yard. The points guard, unaware of the changed schedule, expected to welcome freight train 8572 next and thus left the points at the entrance of the station set to “turn” rather than “straight through”. Express train #51b departs Bellinzona station northbound under a green signal at 2:25am, the local dispatcher only learns of the changed schedule after the train leaves the station. He could have ensured that everything was to proceed as planned before dispatching the train but had chosen not to.

The driver’s assistant in the leading locomotive on train #70 spots a red signal as the train approaches Bellinzona’s freight yard from the north and tells the driver to apply the brakes. His demand is shot down with the driver pointing out that the signal is meant only for freight trains as it guards the turn-off into the freight yard. Plus, the driver can see Bellinzona station’s green entry signal beyond it in the distance. A few seconds later the driver realizes that the points ahead of the train are set to “turn”, proving that the signal did apply to him, and applies the brakes after all, starting to slow the train down. The oncoming express train comes into view just a moment later, and the men realize they acted too late. The southbound train crosses into the oncoming track on its way through the freight yard, slowing down to 40kph/25mph. The leading locomotive’s driver’s assistant manages to jump off the train at the last second before the two express trains collide head-on at the southern end of Bellinzona’s freight yard. The four locomotives are jammed into one-another, with the northbound train’s leading two cars being compressed between the locomotives and the following passenger cars. The gas tanks on AB4ü rupture as the wooden train car is obliterated, the escaping gas immediately ignites and engulfs the following passenger car in a fireball.

15 people die in the collision (some sources claim up to 21), including three train drivers and a stowaway aboard train #51b’s heater car. Train #70’s leading locomotive’s driver’s assistant jumped off just in time, avoiding both the destruction of the driver’s cab and the ensuing fire behind the locomotives, escaping the carnage with minor injuries. How many passengers were injured in total is unknown, 10 people are listed as having survived with severe injuries.

Despite being completely obliterated at least one passenger survives aboard the wooden passenger car (having been last spotted seated inside it according to witness statements), escaping the destroyed train car before the forward part of train #51b is consumed by flames, leaving little of the largely wooden debris that used to be the leading passenger car. On the southbound train the luggage car and the heater car act as a crumple zone of sorts, aided by the identical steel construction train cars holding up much better than their older wooden counterpart. The train’s drivers die in the collision, but there are no fatalities among the southbound train’s passengers.

Investigators soon pointed out that Bellinzona was being upgraded to an electric signal box, which lead to some temporarily incomplete configurations among the signaling-system. Among them was that the stations’ and the freight yard’s entrance-signal apparently weren’t linked to each other or the points. Perhaps the signal had not been red but green, erroneously sending the southbound train into the other train’s path. But with no evidence for the theory and the surviving driver’s assistant insisting that the signal had been red the search for the main cause continued. Also, the SBB pointed out that the lacking wiring alone could not have caused the accident, requiring further errors or defects as the signals were still fully operational, just independently. If the signals had been the sole issue train #70 would’ve crossed through the freight yard and likely slightly overshot its stop at Bellinzona station, nothing more. That is if the points had been set to “straight ahead”. Thus, attention turned to the points guard on duty, who explained that he was expecting two freight trains in relatively quick succession. No one had notified him of freight train 8572’s delay, or of the changed scheduling for the trains with the expected freight train being overtaken by the express train at Ambri-Piotta. He had done nothing wrong based on the information available to him and wasn’t to blame for being given incomplete information, relieving him of responsibility for the collision.

The northbound train’s locomotives (left) and the burned shell of the third car (right), with two cars between them reduced to rubble.

Soon the blame was largely centered on Ambri-Piotta’s dispatcher, who had failed to notify all the required people for the decision to move the overtaking-location to his station. This led to Bellinzona’s points guard having outdated/incomplete information, which led to the points being set to “turn” as the express train approached (instead of the expected freight train), which led to an unexpected red signal which the southbound train’s driver disregarded as being “only for freight trains”, likely thinking it referred simply to the points not being set to turn yet. However, it also has to be considered that the situation could only come to existence due to the massive delay carried by both train #51b (46 Minutes) and freight train #8572 (55 Minutes). Had #51b been on time it would have been joined up with #51a and passed the site of the accident well ahead of the freight train. Had the points guard been given accurate information by the dispatcher at Bellinzona (who was only notified (too) late) he would not have left the points set to “turn”. And had the driver of the southbound train not disregarded the red signal, his train might have stopped in time, at the very least lessening the consequences of a collision.

The remains of train #51b’s boiler car and locomotives (left/center) with train #70’s leading locomotive visible in the distance (right).

The accident’s outcome was significantly worsened by the gas carried aboard train #51b’s leading passenger car, which the old train car required for its interior lighting. The two lengthy tanks ruptured as the collision tore the train car apart, spilling gas which was then most likely ignited by sparks from the overhead catenary (although contact with the boiler in the car ahead is also a possible cause), lighting the following passenger car (which had survived the collision structurally intact) on fire. The fire not only caused a number of injuries and possibly deaths (causes of death aren’t known), it also made identification of the victims difficult.

24 years prior two trains had collided near Mülheim (Germany), claiming 12 lives in an accident whose outcome had been made significantly worse due to gas leaking from similar train cars and igniting on the steam-locomotive’s firebox. After that accident various European railways had started banning gas lit train cars in favor of safer electrical light. Switzerland had held out, especially concerning foreign cars passing into/through Switzerland, but banned gas lit train cars from their tracks entirely immediately after the accident citing the increased risk of a fire caused by the then-new overhead catenary.

The remains of a burned-out passenger car after the collision at Mülheim, Germany.

After the accident the SBB introduced new guidelines saying that signals along a train’s path can only be set to green once all points are set in the correct direction. At the time of the accident the station’s entrance-signal was green expecting the passenger train, but should have been red as the points at the entrance to the freight yard, which were part of the train’s active path, weren’t set correctly for the passenger train. Furthermore, the accident started the development of Integra-Signum, the Swiss train control system which would stop trains from running a red signal the way train #70 did, making the accident far less likely to repeat. The system was eventually introduced in 1933, remaining in service until it was replaced by a new standardized European system in 2018.

A Swiss pre-signal with the new Integra-Signum-system (the boxes by the trails). The system autonomously detects trains running a red signal and stops them.

Among the dead was a German right-wing politician, who’s death in the accident led to some extremist press claiming that the accident had been caused on purpose by Freemasons wanting to get rid of him. A frankly ridiculous claim, which was quickly shut down by the official investigation.

With new guidelines, advanced signaling-systems and automatic train control systems a repeat of the accident is impossible, and the absence of gas heating on remotely modern train cars takes away the cause of the ensuing fire.

The four locomotives were severely damaged in the accident, but due to their almost-new status and the high demand all 4 were repaired, receiving entirely new driver’s cabs. The Be 4/7 ended up being a needless headache for the SBB, with no large order ever being placed and the existing 6 units suffering repeated suspension issues before being retired by 1976. One unit survives today, being used for occasional historic trains. The Be 4/6 was a much bigger success, despite the connecting-rod system proving inferior to the 4/7’s system. It is likely that the former was preferred at the time due to the latter’s system being relatively new and unknown, feeding insecurities. Forty 4/6 were made in total, remaining in service until 1976 despite being relatively unpopular with drivers. Four units remain in historic care today, one of which being operational.

SBB Be 4/6 12320, the sole operational survivor, pulling an enthusiasts’ train in Winter 2021.

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Max S

Max S

Train crash reports and analysis, published weekly.