replacing switch

A replacing switch is a temporary steel structure that sits astride railway rails to create a passable surface over a derailment site. It consists of two parallel iron plates, each shaped to fit the rail head and gauge of the track, bolted together at a fixed distance apart. The assembly bridges the gap between rails where a wagon or carriage has left the track, allowing that vehicle to be drawn back onto the rails by locomotive or winch without further damage to wheel treads or axles.

The plates are typically cast or forged iron, heavy enough to support the weight of rolling stock without deflecting significantly under load. Standard gauges determine the distance between plates: a meter gauge set will differ from a broad gauge or narrow gauge equivalent. The top surfaces are often ribbed or have a slightly raised profile to prevent wheels from sliding sideways during recovery operations. Each plate must seat firmly on both rails simultaneously to distribute load evenly and prevent tilting.

Deployment and variants

Replacing switches are positioned manually or with mechanical assistance at the site of derailment, typically after the vehicle has come to rest. Two or more switches may be used in sequence if recovery requires the derailed stock to travel any distance over damaged track. Some designs incorporate adjustable elements to accommodate minor variations in track geometry or gauge wear. Portable versions weigh several tonnes, requiring railway workshop staff and equipment to transport and install them on site.

The name reflects the device's function: it acts as a temporary replacement for the normal condition of rails and sleepers, allowing stock to pass where normal track has failed. It is distinct from a portable ramp or skid plate used in road transport, as it must precisely match railway gauge and cope with the forces and geometries specific to rail vehicles. Proper installation is critical, as misalignment can damage wheel rims or lead to a second derailment during recovery.