Iron sleepers are metal infrastructure elements made of steel or wrought iron, placed between the rails to secure them and evenly distribute loads onto the ballast. Also commonly referred to as “steel sleepers,” this system played a significant role in the early railway era due to its high strength and recyclability.

Historical Background

Iron sleepers began to be used particularly in Europe in the 19th century and were widely implemented in many countries until the early 20th century. However, with the development of wooden and later concrete sleepers, their usage declined over time. After using iron sleepers for a long period, TCDD also transitioned to modern concrete sleeper systems.

Use of Iron Sleepers

According to TCDD’s 2013 Sector Report, while the share of concrete sleepers in Türkiye’s railway network has significantly increased, the proportion of iron sleepers has declined to around 9%. These sleepers are still used on some lines, but they have largely been replaced by modern systems, especially on heavy freight and high-speed lines. According to the 2023 Network Statement, iron sleepers now exist only on low-density, older track segments and are planned to be gradually replaced under maintenance and renewal programs.

Technical Specifications

Material: Galvanized steel, wrought iron, or rolled products
Length: Typically 260–270 cm
Weight: Between 70–90 kg (depending on steel density)
Fastening: Secured to the rails with specialized bolt systems
Corrosion Protection: Provided by galvanization or painting
Service Life: On average 20–25 years, depending on environmental conditions

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Areas of Use

Secondary lines and connection routes
In-plant industrial rail systems
Temporary lines
Converted systems from old European railways

Advantages

High load-carrying capacity
Fire resistance
Recyclable structure
Standardizable production

Limitations

Electrical conductivity: Incompatible with signaling systems
Corrosion risk: May rust in humid and salty environments
Vibration transmission: Less damping compared to concrete or wooden sleepers
Low rail retention: Rails are more likely to loosen over time

Standards

UIC 864-3: International technical standard for steel sleepers
TS EN 13232-1: Railway superstructure components — Specifications for steel parts
TCDD Technical Specification: Manufacturing and application principles for iron sleepers

Iron sleepers have held an important place in the history of Türkiye’s railways, though their area of use has significantly diminished today. Especially due to their incompatibility with signaling systems and corrosion issues, they have fallen behind concrete and wooden sleepers. However, with appropriate engineering solutions, they are still considered a functional infrastructure component in certain applications.

Iron Sleepers