Wheel–rail interface

The wheel–rail interface is the area of contact between wheels and rails of railways.^[1] The interaction between wheel and rail is a specialized subject covering the design and management of the high stresses in the small contact area between a steel wheel and a steel rail. The focus is on safety improvement, maintenance and replacement costs reduction, downtime reduction, and energy and environmental management.^[2][3] The surface of the wheel that rests on the rail is known as the tread. A wheel may have either a single flange on the gauge side of the rail or two flanges, one on each side of the rail.