Concrete or wooden sleepers are kept below the railway line so that the weight of passing train is spread over a large area of ground and the track may not sink into the ground.

Concrete sleepers, also known as railroad ties, serve several critical structural functions in a railway system. Their primary purpose is to transfer and distribute the massive load of a passing train from the rails to the underlying ballast and subgrade. By providing a wider surface area, they significantly reduce the pressure exerted on the ground, preventing the track from sinking or shifting under the weight of the train (P=F/A). Beyond load distribution, concrete sleepers act as rigid spacers that maintain the correct track gauge (the distance between the two rails), ensuring the wheels remain safely on the tracks. Unlike older wooden sleepers, concrete is highly resistant to rot, fire, and chemical degradation, offering a lifespan of up to 50 years. Their significant weight also adds "lateral stability" to the track, which is essential for high-speed rail and preventing "track buckling" during extreme heat. In modern 2026 engineering, concrete sleepers are often preferred for their ability to handle heavier axle loads and provide a smoother, more durable foundation for long-distance travel.