What is the purpose of a rail?
Jan 15, 2026
What is the purpose of a rail?
Steel rails are an integral part of railway tracks. Together with railway sleepers, rail joints, spikes, clips, bolts and pads, they support the track system and guide the train. The primary purpose of a rail is to guide the wheels of locomotives and rolling stock along a defined path and to provide a continuous, smooth rolling surface that ensures stability and prevents derailment.
Functions of the rail components
| Rail component | Function |
|---|---|
| Rail head | Supports the train wheel load and guides the wheels |
| Rail web | Transfers load from head to foot and provides vertical strength |
| Rail foot | Secures the rail to sleepers and distributes load over a wider area |
The cross-sectional design of the rail also ensures wheel alignment, smooth operation with minimal rolling resistance, and constant track gauge between the two rails.
How do rails transfer loads to sleepers?
Rails transfer the vertical and lateral forces from train wheels to the underlying sleepers, distributing the weight evenly to protect the track bed and prevent deformation. The load path is: wheel to rail head, through the web, into the foot, then through the baseplate or pad into the sleeper and ballast.
| Rail type | Load character | Typical service |
|---|---|---|
| Heavy rail (60-75 kg/m) | High loads | Mainline passenger and freight trains |
| Crane rail (QU70-QU120) | High concentrated point loads | Industrial cranes and ports |
| Light rail (8-30 kg/m) | Low to medium loads | Urban transit, mining and industrial tracks |
International rail series
Rails are manufactured to many national and international standards so that dimensions and fastening systems remain compatible across projects:
| Series | Origin | Common sections | Materials | Lengths | Reference standard |
|---|---|---|---|---|---|
| A Series | German | A45, A55, A65, A75, A100, A120, A150 | 50Mn, U71Mn | 10/12/15 m | DIN 536 |
| ASCE Series | American | ASCE 25, 40, 60, 75, 85, 90, 115, 136 | 700, 900A, 1100 | 6-12 m, 12-25 m | ASTM, AREMA |
| UIC Series | International Union of Railways | UIC 50, 54, 60 | 900A, 1100 | 12-25 m | UIC 860-0, EN 13674-1 |
| BS Series | British | BS50O, BS60A, BS60R, BS75A, BS75R, BS80A, BS100A, BS113A | 700, 900A | 8-25 m | BS 11-1985 |
| JIS Series | Japanese | 15 kg, 22 kg, 30A, 37A, 50N, CR73, CR100 | Per JIS | 9-10 m | JIS E1103 / E1101 |
| AS Series | Australian | 31, 41, 47, 50, 53, 60, 66, 68, 73, 86, 89 kg | 900A, 1100 | 8-25 m | AS 1085 |
| ISCOR Series | South African | 15, 22, 30, 40, 48, 57 kg | 700, 900A | 9-25 m | ISCOR |
FAQ
Why does a rail have a head, web and foot?
The head carries the wheel and guides it, the web gives vertical bending strength, and the foot spreads the load onto the sleeper and ballast; each part is shaped to optimize one function.
How does the rail prevent derailment?
The head profile and the wheel flange interaction keep the wheels aligned on the rail, while the constant gauge between the two rails holds the track geometry.
What is the difference between crane rail and mainline rail?
Crane rail has a wider head and thicker web to carry concentrated wheel loads from crane trolleys, while mainline rail balances wear, fatigue and ride quality for high-speed traffic.
Which standard series covers European mainline rails?
The UIC 860-0 and EN 13674-1 series cover European mainline sections such as UIC 54 and UIC 60.
Why do rail standards specify lengths?
Standard lengths control joint spacing, transport handling and welding logistics; 12-25 m lengths are typical for mainline rail, while 6-10 m suits light and mining rail.
What happens if rail gauge is not maintained?
Wheel-rail contact becomes unstable, increasing wear, vibration and the risk of derailment; fasteners and sleepers hold the gauge constant.
