Wales train crash: leaf fall and digital signalling are possible areas of inquiry

The tragic train accident involving two trains near Talerddig and Llanbrynmair in rural Wales on Monday evening stands out as an uncommon event in the UK's recent railway history. There have been no head-on collisions this century, and only one passenger fatality has occurred in train accidents across the UK since 2007.

Inspectors from the Rail Accident Investigation Branch (RAIB) arrived at the Powys site on Monday night and continued their work during the day. They are expected to publish an initial report later this week.

Although any conclusions made prior to the formal investigation are merely assumptions, the accounts from witnesses about a train that couldn't halt, combined with its low speed and the season, suggest that fallen leaves could be an important factor to explore, particularly because the railway runs through a heavily wooded area in Powys.

According to Network Rail, leaves on the tracks are similar to black ice on roadways. During the autumn season, dedicated trains are deployed daily, and even more frequently if needed, to clear leaves off the rails.

The remarkable testimonies from passengers who saw the driver heading towards the carriage, telling them to prepare for impact, highlight the slow speed of the crash—probably under 20mph—and raise concerns that at least one of the trains may have been unable to be controlled.

The event took place roughly 900 meters (1,000 yards) past a passing loop where the train heading to Aberystwyth was supposed to halt and let the other train go by. Instead, it continued on without stopping until it reached the collision site.

The most recent passenger train crash in the UK occurred in Salisbury during the fall of 2021. Investigators determined that the accident was triggered by leaves on the tracks, which impacted the driver's ability to stop the train in time. Despite efforts to brake, the train continued through a red signal while facing strong winds and heavy rain.

Another area worth exploring could be the Cambrian line, where two small Transport for Wales sprinter trains collided. Even though this route is mainly single-tracked and cuts through some of the sparsely populated regions of Britain, it is equipped with some of the most advanced signaling technology available.

It served as the initial test for implementing digital signaling and train control systems called the European Rail Traffic Management System (ERTMS) and the European Train Control System (ETCS). These systems are currently being set up on the east coast mainline that connects London to Edinburgh, about ten years after they became active in mid-Wales. This upgrade significantly reduces the chances of accidents caused by mistakes from signallers or drivers, as trains are designed to automatically apply brakes if they detect another train ahead, even if the driver does not respond in time.

However, this system has already been examined in earlier reports by the RAIB. In October 2017, an investigation took place regarding a significant data loss on the Cambrian line. This issue arose when temporary speed limits, caused by adverse weather conditions, were not communicated effectively, leading to trains traveling faster than the safety thresholds.

No matter what led to the accident, it marks yet another unfortunate incident in the UK railway system, which has generally maintained a solid safety track record. Over the past twenty years, following a series of disastrous accidents during the initial years of privatization under Railtrack from 1999 to 2002, there has been a significant emphasis on safety, resulting in many years without any passenger fatalities.

Trains continue to be the safest way to travel. While investigations on the Welsh railway were back underway on Tuesday morning, the M6 motorway faced yet another closure due to a car accident.

Nonetheless, this recent event occurs just three years after the Salisbury crash, and if fallen leaves turn out to be the cause, it will once again draw attention to Network Rail's strict cleaning procedures during the autumn season.

This also comes after the Stonehaven accident in 2020, which occurred when heavy rain and inadequate drainage caused a ScotRail train to derail, resulting in the deaths of three individuals, including the train driver and a guard. This incident raised concerns about the need for increased investment in Britain’s railway infrastructure to safeguard against increasingly severe weather and the impacts of climate change.

Rail experts often emphasize how they never overlooked their impressive safety record, especially considering it had been over ten years without any accidents. However, experiencing three crashes in just four years creates a sense of concern.