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Climate & transportationKeeping the trains running on time in the face of climate change

Published 6 September 2017

There are many railway bridges around the world. In the United Kingdom alone there are more than 40,000 railway bridges. Each nation has employed its own methodology for maintenance and repairs of this essential infrastructure, but new, daunting challenges created by climate change — extreme heat, extreme cold, and severe flooding — require yet more rigorous solutions.

Physicist Michio Kaku once said, “What we usually consider as impossible are simply engineering problems… there’s no law of physics preventing them.” And so, it has been with railway and metro bridges that span waterways. The city of Washington, D.C., is bounded on two sides by rivers and an untold number of streams. Every morning the Orange Line, one of six train lines that serve the city, ferries 12,060 commuters — per hour. And this miracle occurs every day in Berlin, Tokyo, London, Amsterdam, Shanghai, and numerous other metropolitan areas. In the United Kingdom alone there are more than 40,000 railway bridges.

Much has been written on how to maintain this infrastructure, particularly in the difficult transition zones where trains leave land to ascend bridges over water. “All railway systems suffer rapid track deterioration at the transition zones requiring high maintenance costs,” said Sakdirat Kaewunruen of the Department of Civil Engineering, University of Birmingham, United Kingdom. “In the past decades, there have been so many ad hoc solutions provided, but there has been no work on evaluating its life cycle cost and sustainability.”

Each nation has employed its own methodology for maintenance and repairs, but new, daunting challenges created by climate change — extreme heat, extreme cold, and severe flooding — require yet more rigorous solutions.

A study titled, “Lifecycle Assessments of Railway Bridge Transitions Exposed to Extreme Events,” published in Frontiers in Built Environment, benchmarks the costs and carbon emissions for the life cycle of eight mitigation measures and reviews these methods for their effectiveness in three types of extreme environmental conditions.

Frontiers notes that railway systems are designed for a 50-year lifespan, which is calculated on the integrity of the materials used, and most railways are built along one of two common track systems: rails set on railway ties (United States) or sleepers (United Kingdom), which are then ‘ballasted’ into beds of rock or gravel; or rails that are set onto concrete slabs. Sometimes both are used on one rail line with one transiting to the other. In either case, the engineering feat that must be solved is that as the train crosses the transition between ground and bridge, the relative stiffness of the bedrock, concrete, vs. metal bridge can impart intense vibrations that drastically impact the train rails and even make the ride uncomfortable to commuters. Transition zones require four to eight times more maintenance than ordinary rail tracks.