Korea Railroad Research Institute commercializes eco-friendly composite rail sleeper, installs it on Busan Metro Line 2

The Korea Railroad Research Institute has commercialized a Circular Composite Sleeper (CCS) and completed its field installation at an aging turnout replacement section on the Yangsan turnback line of Busan Metro Line 2, the institute said.

The CCS is an eco-friendly sleeper that repurposes waste plastic as a structural railway material. Like wood, it can be cut and drilled on-site, making it suitable for special track sections — such as turnouts and rail joints — where fastener positions need to be adjusted.

The sleeper also incorporates glass-fiber-reinforced composite technology, preserving the workability and machinability of conventional wooden sleepers while delivering superior flexural strength, flexural rigidity, ductility and dimensional stability. It is particularly resistant to the main deterioration factors that afflict wooden sleepers — moisture absorption, decay and insect damage — which is expected to improve long-term durability and reduce maintenance burdens.

The installed CCS maintained stable mechanical performance through more than 2 million repeated load cycles in testing. Results showed no structural damage or fracture after repeated loading, with key properties including flexural strength and flexural rigidity remaining consistently intact.

Wooden sleepers have long been used in special track sections such as turnouts and rail joints because they are easy to cut and drill on-site and straightforward to install. However, they have posed growing maintenance challenges due to environmental concerns over preservative treatments such as creosote oil, as well as long-term moisture absorption, wood rot and material degradation.

As the production and use of conventional wooden sleepers becomes increasingly restricted, demand has grown for an alternative sleeper technology that retains on-site workability while improving durability and environmental performance.

The institute expects the CCS to spread beyond replacing aging wooden sleepers, finding application as a sustainable composite sleeper technology across a range of settings — including bridge sections, turnouts, rail joints, industrial railways and special sections of urban transit systems.

"The sleeper is lighter than concrete sleepers, which improves workability on bridges, aging structures and sections with restricted equipment access," said Kim Ji-hwan, a senior researcher at the institute. "We will continue to verify CCS performance through long-term monitoring and field feedback, and pursue further technology development to expand its application."