Background
Sihlbrugg is a town of just 20 permanent residents in northern Switzerland, located in the Canton of Zug 16km/10mi south of Zürich and 8km/5mi north-northeast of the city of Zug (both measurements in linear distance).
The town’s documentation goes back around 800 years and points to its creation stemming from the location on the Gotthard-route, at an intersection of a few paths enabled by a bridge over the Sihl river (“Sihlbrugg” can be translated to “Bridge on the Sihl”). Today the town is still an important intersection between different roads and railway lines, somewhat explaining why the town mostly consists of commercial properties and a few hotels with very few residential buildings. Located a short distance north of the town itself is Sihlbrugg station, a stop on the Thalwil–Arth-Goldau railway which is a 32.9km/20.5mi) partially single track electrified branch line feeding the Gotthard Railway. Immediately south of the station lies the 3.36km/2mi single track Albistunnel, with the topography of the area necessitating the slight separation of the town and its station. Opening in 1897 the line sees mostly regional passenger services with the occasional national express train. The single-track character of certain stretches makes traffic on the line rather susceptible to delays, especially with occasional mudslides or rockfall blocking sections of track. Stations like Sihlbrugg are bottlenecks of sorts, being the last respectively first chance for trains to pass one another ahead of/after a longer single track section.
The trains involved
In the weeks before the accident (and scheduled to continue after) workers had been replacing some of the track in the Albistunnel south of Sihlbrugg station, using the station as a base of operations. Involved in the work was a material train including two type Faccs four-axle ballast cars at the back of the train. The cars, owned by On Rail, a German railway equipment provider. The cars measure 14.86m/48.75ft in length at a weight of 23 metric tons empty and can each load about 56 metric tons. The rear four cars of the construction train were coupled together as they were parked up on a siding, being nearly right up against the next 3 cars. All the parked cars had the brakes applied.
Train 30162 was a historic steam train from Arth-Goldau to Zürich main station provided by the Zürcher Museumsbahn (“Zürich historic railway”) ZMB, a private enthusiast group founded in 1996 to preserve historic trains once used in the area. Leading the train was UeBB CZm 1/2 number 31, a historic two axle steam railcar made in 1902 and now owned by the SBB’s (Swiss national railway) historic department. The railcar measures 11m/36ft in length at a weight of 21 metric tons and can reach a top speed of 45kph/28mph. The car offers 30 seats and is driven by a crew of two, just like most steam engines. After being restored in 1980 the railcar, the sole survivor of its type, was kept operational and is regularly used for historic tours.
On the day of the accident the railcar was pulling a single third class passenger car type C22 made in 1892. The car, owned by the ZMB, measures 10.7m/35ft in length at a weight of 10 metric tons empty and can carry as many as 50 passengers at up to 60kph/37mph.
The accident
On the 18th of February 2016 at 11:23pm shunting-work at Sihlbrugg station in connection with the construction work in the adjacent Albistunnel finished up with a set of 4 freight cars being pushed from track 42 (note that this doesn’t mean there are 42 tracks at the station, track 42 is labelled track 2) into a dead-end siding at the northern end of the station. At 5:00am the next morning the construction coordinator radioed dispatch that the overhead wires could be turned on again. The dispatcher he reached in return asked if the tracks in the tunnel and at the station (except for the siding) were clear. The coordinator replied that the tunnel was clear. Only getting half his answer the dispatcher inquired again about the station, specifically track 42 and the points number 4 which connected the track 42, the siding (which track 42 turned into past the points) and the neighboring track (which exits the station towards Zürich). The coordinator announced that he was going to go check, and replied a few seconds later that everything was “fine”, repeating the reply when the dispatcher asked specifically about points number 4. The dispatcher thus set the points to send trains from track 42 towards the station exit rather than into the occupied siding. There was no traffic using the points for the following hours.
On the 20th of February 2016 at 9:45pm historic train 30162 left Arth-Goldau for Zürich with 56 passengers. Driving the train was a crew of 3 train drivers, one driving the train, one acting as a stoker and a third man acting as a driver’s assistant. The driver and stoker were both certified train drivers with the SBB, the assistant was a retired SBB train driver. SBB Historic tours are done by SBB-staff in their off-time. By the time the small steam train chugged through the Albistunnel the rail car had almost used up the water in its tank, necessitating a stop at Sihlbrugg station which the train reached at approximately 10:30pm. After filling up the driver contacted dispatch at 10:40pm, speaking to a different dispatcher than the construction coordinator the night before, and was cleared for departure. The three men in the cab of the historic train confirmed the setting of the exit-signal among them and the driver started to accelerate. A few seconds later the stoker saw the silhouette of a freight car protruding into the historic train’s path, past the signal but just barely ahead of the points. He triggered an emergency stop and shouted a warning to his coworkers, a moment later the steam train struck the parked freight train’s rear car at 22kph/14mph. The impact pushed the parked freight cars back approximately 1m/3ft, derailing the historic passenger car and two axles on each of the rear two freight cars. The front of the rail car slightly caved on impact with the much sturdier freight train while the passenger car climbed the rear of the rail car, causing severe damage to the rear entrance-area. Two crew members and 18 passengers suffered injuries as the train stopped with a violent jolt, two of which being severely injured.
Aftermath
The passengers who didn’t require hospitalization continued their journey shortly after the accident with a regular train, buses or by being picked up by relatives, leaving the site to the investigators. An initial suspicion was a technical defect on the 100+ years old train, maybe it had departed on accident or the brakes hadn’t applied properly. But the train was in perfect shape, with no trace of any defect found. Interviewing the dispatcher and the train’s crew along with reviewing records revealed that the dispatcher on duty the previous night had received faulty information from the construction crew, forwarding it to the dispatcher working the night of the accident. The freight train hadn’t been parked properly, being split up into groups of freight cars with gaps in between them. This meant that the rear car ever so slightly protruded into the points number 4, blocking the path for the departing train. But when investigators calculated the length of the freight train without gaps they found that it still would’ve been too long for the siding. The points feature an axle-counter to ensure trains clear them before they are moved, however, after being told everything was clear the first dispatcher reset the counter to allow normal operations over the points. A small signal (ZS32A) marks the end of the “parking zone” on the siding, before the collision the two rear cars of the freight train were entirely past the signal (where they were not allowed to be parked).
Sihlbrugg station features no artificial lighting, so with the steam train parked at the other end of the station to fill up with water the crew couldn’t see the parked freight train, not even with the (admittedly rather dim) headlights of the railcar. By the time the train cars came into view it was too late to stop. Investigators went over the radio-conversations again, and traced the steps of the coordinator the night of the accident. The result was rather clear, in that he made up his replies. In the time between his statements he couldn’t walk from his position in a container-office (approximately 120m/394ft) over to the points, check if they’re clear, and respond. Apparently he had just said he was going to check them, waited a few seconds and then replied what he thought was the truth/should be the truth, likely without leaving his office. The guidelines said that the coordinator was sufficiently educated on the site to be trusted, the dispatcher did not have to walk over to the points and check himself, so he couldn’t be blamed for following the usual routine when he had no reason to doubt the coordinator.
The freight cars suffered minor damage in the collision, as did the tracks, while the steam train suffered severe damage estimated at 500 thousand Swiss Francs/463 thousand Euros/ 537 thousand USD. There is no record of a trial or sentence of any sort, so it has to be assumed that the matter was handled internally by the company doing the construction work. The historic train could be repaired/rebuilt after the accident, and is still in operation today with no sign of the damage having been there. This was the first actual accident in the railcar’s history, except for a few minor derailments in the past (before it became an operational museum piece).
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