Keeping the trains running on time in the face of climate change

The study investigates mitigation measures for bridges that span 30 meters and 100 meters. The study reviews the eight most common techniques for bridge transitions, including: under ballast mats (UBMs), soft baseplates, under sleeper pads (USPs), rail pads, embankment treatments, transition slabs, ballast bonding, and wide sleepers. Overall, the study finds that elastic rail pads, soft baseplates, and UBMS are most suitable for short-span bridges, relying on a range of materials such as elastic materials, chloroprene rubber, or polymeric compounds to provide reduce railway stiffness. Unfortunately, the same materials that provide elasticity deteriorate faster in extreme heat and extreme cold, conditions that have become more frequent with climate change. For reference, the materials tend to exhibit sensitivity at 20 degrees C and severe problems in the dead of winter at -40 degrees C in the far northern latitudes.

For long bridges, the authors recommended employing transition slabs, ballast bonding, and embankment treatments — methods that mitigate track stiffness gradually with longer transitions. These solutions tend to be greatly affected by flash flooding that can wash away embankments and ballast that supports the track structure. In some areas of Norway flooding has turned sediments into mud causing train tracks to collapse.

Global warming and climate change… increase the renewal and wear rates of lubrication materials, as well as the possibility of track twisting and buckling,” said Kaewunruen in an earlier paper with Lei Wu, who is currently working on the Kuala Lumpur-Singapore High Speed Railway.

In this study, the authors provide engineering assumptions and sample calculations for their recommendations, but also stress that solutions need to be developed on a case-by-case basis, taking into account cost over the life cycle, environmental factors, and the impact high maintenance can have on the carbon footprint. Furthermore, cost of materials and of maintenance can range widely from country to country.

Climate change is a significant issue for every industry in the world,” said Kaewunruen. “Next we will analyze scenarios with multiple hazards. We have been informed that some events may come together, for example an earthquake at the same time as extreme heat, or extreme wind at the same time as extreme rainfall or runoff. Bridges respond to different events individually, but when you have multiple hazards simultaneously they can suffer even greater impacts.”

— Read more in Sadudee Setsobhonkul et al., “Lifecycle Assessments of Railway Bridge Transitions Exposed to Extreme Climate Events,” Frontiers in Built Environment (19 June 2017) (DOI: 10.3389/fbuil.2017.00035)