derailers

A derailer is a safety device installed on railway tracks to intentionally derail a vehicle if it moves onto a restricted or protected section of track. Derailers are used to prevent collisions, protect yards and maintenance areas, and guide runaway or unauthorized rolling stock away from active main lines or personnel.

Construction and operation

Most derailers consist of a rigid metal component that projects into the rail or lies across the track, designed to interact with a wheel flange as a car passes. When a wheel encounters the derailer, the wheel is steered off the rail surface and guided off the track, typically onto a safe area or an adjacent track. Some derailers are fixed installations, while others are portable and can be moved for maintenance or special operations. In some systems, derailers are actuated by mechanical, electrical, or hydraulic means to enable or disable protection as needed.

Types and placement

Permanent fixed derailers are placed at points where derailment would prevent access to sensitive tracks, yards, or stations. Portable or temporary derailers are used during construction work, testing, or when a temporary safety perimeter is required. Derailers vary in aggressiveness and are chosen based on rolling stock wheel profiles and local operating procedures to balance effectiveness with potential equipment damage.

Safety and limitations

Derailers are a last line of defense and are not substitutes for proper braking, locking, or securement of equipment. They require regular inspection and maintenance to ensure correct alignment and operation. Potential equipment damage is a consideration in their placement and use.

History and context

Derailers have been employed in rail safety practices for many decades and are widely used in rail networks where controlled access to certain tracks or zones is necessary.