points

Points are the mechanical assembly that allows a train to move from one railway line to another. They consist of two movable rails, called blades or tongues, that pivot at one end and can be positioned to guide wheels onto either of two diverging tracks. The blades are held in place by a lock mechanism and operated by a switch mechanism, either manual or powered, usually located in a signal box or modern control room.

The geometry matters. Each blade tapers from full rail section at its free (moving) end down to a thin edge, typically 10 to 12 millimeters at the toe, to fit smoothly between the stock rails without creating a gap that could derail a wheel. The stock rails are the two fixed rails that form the converging tracks upstream of the switch. Correct blade angle and radius ensure smooth passage at line speed without shock loading.

Points are classified by their configuration: single slip points route traffic in one direction only; double slip points allow routing in both directions at the same location. Diamond crossings are a separate mechanism that allow crossing traffic without a switch. The rail gauge (distance between rails) and the radius of the diverging route both determine the sharpness of the angle the blades must create, which affects the maximum safe speed through the points.

Maintenance and failure modes

Points jam because of ice, debris, or corrosion on the blades and stock rails. Frost heave or settlement of the trackbed can misalign blades so they no longer make full contact with stock rails, creating a hazardous flange way gap. Wear flats on blade edges reduce guiding ability. Broken heels, where the fixed end of a blade fractures, are rare but cause immediate failure. Regular inspection, lubrication, and realignment are essential; electrified points with heated rails are used in severe climates to prevent ice formation.

The term comes from the pointed geometry of the taper on the blade rails. In North American usage the same device is called a turnout or switch, while points is standard in British, European, and Commonwealth railway terminology. The powered machinery that moves the points is called a point machine or point motor, usually electro-hydraulic or electro-mechanical in modern installations.