99.9 Percent is 75 Percent: The 2016 Hermalle-sous-Huy (Belgium) Train Collision
Background
Hermalle-sous-Huy is a town of 1519 people (as of 2021) in eastern Belgium, located in the Wallonia-Region 17km/11mi west-southwest of Liège and 76km/47.5mi east-southeast of Brussels.
The town lies on the Belgian Railway Line 125, a 60km/37mi double-tracked electrified main line connecting Liège with Namur. Opening in 1851 the line sees all sorts of railway services, with the exception of high speed trains which have mostly moved to dedicated high speed lines that head to Brussels further north. It is also part of an important freight corridor connecting the industry and harbors of northern France along with the local Dolomite with the industry-heavy German Ruhr-area. The line is rated for speeds of up to 120kph/75mph.
The trains involved
Travelling eastbound on the line was a freight train provided by B-Logistics, consisting of two Belgian Railways (NMBS/SNCB) class 28 electric locomotives and 30 type Falns ballast cars owned by Ermewa filled with Limestone heading to Aachen (Germany). Introduced in 1987 the type Falns ballast cars are a four-axle open top bottom-unloading design that can be found all over Europe, having become one of the most common types of ballast car in use. Each car has an empty weight of 23.5 metric tons at a length of 12.54m/41ft and an carry up to 64.5 metric tons at speeds of up to 120kph/75mph.
Following behind the freight train was SNCB passenger service number E3820, an Intercity service from Mouscron to Liers-Herstal. The train consisted of two NMBS/SNCB AM 96-series multi-system electric multiple units. Introduced in 1996 the Series 96 is a three-car electric multiple unit measuring 79.2m/260ft in length at a weight of 175 metric tons. Each unit can carry 213 passengers in a two-class configuration at up to 160kph/99mph. The type was developed with multi-traction use in mind, leading to the integration of rubber passageway-seals on the end cars (giving them the charming nickname “toilet seat”) and a control desk that can fold out of the way when two units are combined to one train. That design was previously found on Danish type-MF multiple units, leading to some calling the series 96 the “Danish nose”.
The train involved in the accident consisted of unit 548 (leading) and unit 461 (trailing), and carried around 40 people at the time of the collision, many of whom were students headed to Liège.
The accident
The 5th of June 2016 was marked by heavy thunderstorms hitting the area around Hermalle-sous-Huy, with a lightning strike eventually hitting a control unit for the track occupancy system. The track occupancy system functions (in simplified terms) by a sending-unit introducing a low current to the rails and a measuring-unit at the end of each block-section (stretches of track that only one train may occupy at a time) measuring the current. If the track is empty the current that is sent is the same as the one being received and the section registers as “free”. If a train enters the section the current goes through the train’s wheels, creating a short-circuit and thus changing what is received , leading to the section registering as “occupied” and signals for following trains being switched to red to ensure a safe distance.
With the track occupancy system being out of service traffic on the affected sections (three block-sections were shut down) was halted and technicians were dispatched to fix the damage. The first section was back to operation by 8:50pm, the second by 10pm, and the third was intended to be back to operating by 11pm. In the meantime traffic was run at a vastly reduced capacity, with trains having to stop at the red signals and then proceeding at slow speed on sight.
At approximately 10:52pm the B-Logistics freight train approaches the block sections affected by the lightning strike. As the third section’s occupancy detection is still out of service it will have to come to a stop ahead of it, with the pre-signal D.11 showing a double-yellow (“expect stop”). The driver acknowledges the signal by pressing a button for the train control system and begins slowing down, bringing the freight train to a stop just ahead of the B222 main signal, which shows red (an indication that might be wrong). As instructed he notes down the signal-defect and instruction to disregard, takes a photo of the red signal, and sets the train in motion again, aiming for a speed of approximately 13kph/8mph, slow enough to stop his train should another train come into view up ahead.
Following behind the freight train is SNCB E3820, which reaches signal D.11 at 11:01pm. The signal still shows double-yellow, indicating a red signal up ahead. The guidelines for passenger train drivers state that the following is expected when encountering a double-yellow signal:
- Cut power to the traction-motors and beginning a controlled deceleration
- Acknowledge signal in the train control system
- Obeying instructions by the signal and possible additional instructions from dispatch until told otherwise
- Pause any communication with others, in person or via the radio
E3820’s driver does acknowledge the double-yellow in the train control system, but instead of initiating a deceleration he passes the signal at approximately 112kph/70mph. In fact he speeds right through the red B222 as well, only triggering an emergency stop when the back of the freight train comes into view at 11:03pm. Calculations later show that by the time he did so the trains were just 178m/584ft apart, nowhere near enough to slow down to the freight train’s walking pace speed. Seconds after initiating the emergency stop E3820 crashes into the back of the freight train at a speed of 88kph/55mph, instantly collapsing the passenger train’s driver’s cab. The rear of the leading car was momentarily lifted off the tracks, pulling the forward end of the second car with it, before falling back down onto the rail line and falling over. The multiple unit slid to a stop just as ruptured pneumatic lines triggered an emergency stop on the freight train, bringing it to a halt a short distance ahead of the former’s wreckage. The driver of E3820 is killed instantly in the collision, along with two of his passengers. 36 passengers aboard the passenger train are injured, 9 of which severely.
Aftermath
The accident completely locked down Line 125, creating immense chaos as the bad weather had caused disruptions on several surrounding rail lines as well. Responders were on site within minutes, helping with the evacuation of survivors and making sure no passengers wandered off in shock and ended up in the adjacent river. Investigators began their work within a few hours of the accident, examining both trains and recovering the freight train’s data-logger as well as confiscating that of the signaling system. It wasn’t until the eighth of June, when workers cut apart the crushed front end of the passenger train, that the passenger train’s data-logger could be recovered and its data examined. Both trains had been in a section of track with the occupancy detection out of service, but the preserved data along with the freight train driver’s notes and statements from him and the signal box staff proved that the freight train had been operated exactly as instructed, maintaining “stop on sight” speeds until it would leave the block-section. The passenger train, however, clearly had not.
Examination of the passenger train’s wreckage had shown no sign of any defect, a finding confirmed by the data-logger later showing that the train had made very effective use of its braking system, only that the use tragically came too late. Signal disturbance procedures are nothing out of the ordinary and any train driver certified in Belgium knows how to follow them, so soon the investigators had no choice but to place blame on the driver of E3820, concluding that he had knowingly ignored not one but two signals. The investigation couldn’t determine why, with no sign of either the driver becoming incapacitated or willfully ramming the other train, so the exact reasoning is something the driver took to his grave.
But with the “how it happened” cleared up there was one more issue to solve (and regular readers of the blog will know what’s coming). Railways operate by a system of “no single point of failure”, meaning just because of one thing going wrong there cannot be a catastrophic accident, there is to always be a second system, a backup that will “kick in” and keep operations safe. Belgium had enforced the introduction of the “TBL 1+” train protection system following the 2011 Buizingen Train Collision, where 19 people had died after a regional train ran a red signal and caused a head-on collision. TBL 1+ would automatically force a train to stop when running a red signal, and can also observe if a train is slowing down up to 300m/ft ahead of a red signal, something the previous system was not capable of. So, when it came to light that E3820 had sped past a red signal unhindered, people obviously had some questions. Especially because the SNCB had previously claimed that 99.9% of the Belgian rail system are equipped with the new system.
Eventually Mister Lallemand, the SNCB’s CEO at the time, had to admit that, in fact, only about 75% of the rail system were equipped with TBL 1+, and B222’s section of track was not among them. The “99.9%” claim had come from signed contracts for the installation giving a scheduled deadline, but by the time of the accident the contractor had not yet finished the work. Thus, with E3820’s driver acknowledging the signals, there was nothing stopping him from running into the back of the train ahead. Belgium’s traffic minister, Mister Bellot, promised the public that there had been no delays in the introduction of the system, fighting rumors of going for a cheaper but slower introduction of the system, and that they really had done the best they could after the 2011 train collision. The introduction of TBL 1+ was finished a few weeks after the accident, and since December 2016 incompatible trains are banned from Belgian rail lines.
With sole blame being placed on the deceased driver of E3820 there were no legal consequences for anyone involved, and with the introduction of TBL 1+ at the site shortly after the rail line was repaired a repetition of the accident is very unlikely.
History repeats itself
8 years before the accident a very similar accident had occurred just a short distance away, when, after a defect in the signaling-system, the driver of a regional train didn’t proceed with appropriate caution, causing him to collide head-on with a parked freight train. That time 64 people were injured.
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