quadrail

Quadrail refers to a type of railway track configuration that utilizes four rails. This setup is primarily employed to allow for two different gauges of trains to operate on the same track. Typically, a quadrail track consists of two sets of standard gauge rails placed alongside two sets of broader gauge rails, with the inner rails of the broader gauge aligning with the outer rails of the standard gauge.

This system is most commonly found in regions where historical railway networks developed with different track gauges, and where it was more cost-effective to create dual-gauge track than to convert entire lines. For instance, in some parts of Europe and South America, where standard gauge and broader gauges coexist, quadrail allows for seamless transit of trains from different networks without the need for extensive track rebuilding or complex transshipment operations.

The implementation of quadrail requires precise engineering to ensure safe passage for trains of varying wheel spacing. Special designs of wheelsets and signaling systems are often incorporated to manage the dual-gauge operation effectively. While it offers flexibility in connecting different railway systems, quadrail can also present operational complexities and maintenance challenges compared to single-gauge tracks. Its use is a pragmatic solution for bridging historical gauge differences and facilitating inter-network connectivity.