Getting back on track

Rail freight wagons appear sturdy, but uneven distribution of their cargo can literally result in them coming off the rails.

Dr Phil Shackleton

School of Computing and Engineering

Previous research established that this is a prime risk factor for derailments. The industry’s regulator, the Office of Rail and Road (ORR), called for an industry-wide response. A research project commissioned by key players in the rail freight sector formed one part of that response. Dr Phil Shackleton and his team at the University of Huddersfield’s Institute of Railway Research (IRR) were already partners in three EU-funded projects studying freight suspension systems during this time and took on the new research project.

A happy synchronicity

Dr Shackleton explains: “The outputs from the EUfunded projects gave us a better understanding of freight suspension behaviour and the factors that influence it. They helped us develop a modelling approach to investigate and measure variation in risk performance.” The Rail Safety and Standards Board (RSSB) funded his team to specifically study the derailment risk caused by “imbalanced loading” on the freight wagons most commonly used on the UK railway. From 2017, the team spent two years running 6,000 computer simulations of load distribution and track conditions. The team applied metrics they had devised previously to existing data and technology, allowing them to assess the risk factors from uneven loads for different types of freight wagon, train or wagon contents.

Targeted solutions

As a result, they advised the industry on a range of mitigations. These included a warning that capacity in wagons built for a specific purpose – such as carrying coal – should be reduced when they were re-purposed for other freight, particularly aggregates. The coal wagons left redundant by the closure of coal-powered power stations were shortened in light of the University team’s work, a measure that meant they were better-equipped to cope with their new cargo. That innovation alone is thought to have saved around £175m by allowing for the safe repurposing of coal wagons. The Chair of the Cross-Industry Freight Derailment Prevention Group has said the work has extended the life of around 2500 redundant coal wagons. Repurposing each wagon costs £50,000 – well under half the £120,000 cost of a new aggregates wagon.

Dr Shackleton’s team emphasised the importance of even loading of wagons. In response, the freight operating companies developed a range of innovations – including drawing a line down the centre of some wagons to guide those loading them. The industry also revised loading guidelines for shipping containers on intermodal wagons. This rapid response by industry to the research findings produced swift results: the number of reported ‘monthly longitudinal imbalances’ – a key factor in derailments – fell from 70 to just three. Crucially, the ORR removed freight derailments from its list of top five risks in 2020.

Lasting impact and official recognition

Freight derailments have halved in a period when the volume of cargo being carried by rail has risen by around 25%. The work has also significantly reduced the risk of what the regulator had referred to as the perfect storm: the nightmare scenario of a passenger train crashing into a derailed train from an adjacent track. That risk was real given that most derailments occur where lines change track. The work has also shaped the design of new suspension systems for wagons and training for frontline staff on what a balanced load actually looks like in different wagons and for different types of cargo. Her Majesty’s Chief Inspector of Railways, Ian Prosser, said:

“Phil Shackleton’s work provided the incontrovertible evidence, a measurement system and thresholds to allow the freight industry to act on this matter. This has had a great positive impact. It has been an exemplar of how academia can work hand in hand with industry stakeholders to solve a complex problem.”