This supplementary rail is bolted to the inside of the main running rail with a narrow flangeway between them. It physically traps the backside of the wheel flange, preventing the opposite wheel from taking the wrong path through a turnout frog or climbing the rail on sharp curves. By steering the axle firmly through the gap, it prevents devastating derailments in high-risk track sections.
Heard on the job
The geometry car flagged a wide gauge defect right where the check rail bolts to the running rail.
Insider tip
North American trackmen almost exclusively say "guard rail," while "check rail" is the standard term in British and international track engineering.
Also heard as
- guard rail