crosstie

A crosstie, or sleeper in some regions, is a rectangular support that carries railroad rails in a track structure. It sits in the ballast and fixes the rails in place to maintain gauge and alignment, while distributing the load from passing trains into the ballast.

Materials and varieties vary by region and application. Wooden ties have been traditional in many networks, typically made from durable species such as oak or pine and treated with preservatives to resist rot. Concrete ties, introduced in the early to mid-20th century, are widely used for mainline and high-speed service because of their long life and stiffness. Steel and composite ties are also in use, especially in specialized or heavy-haul settings, or where environmental concerns limit wood use. Some regions employ hybrid designs or polymer-based composites to balance weight, durability, and maintenance needs.

Functions and installation. Crossties support the rails and maintain gauge, align the track, and help distribute loads to the ballast and subgrade. They are laid perpendicular to the rails and embedded in ballast, with rails fastened to them by spikes, bolts, or clip systems and tie plates. Fastening systems vary by material and era, with modern clips providing quick, secure rail attachment on concrete ties.

Maintenance and lifespan. Wooden ties typically require replacement after 15–25 years depending on traffic, climate, and treatment; concrete ties last longer, often several decades, though they can crack and wear at fastener points. Regular inspection and replacement of defective ties are standard parts of track maintenance.

See also: sleeper, ballast, track gauge, fastening system.