diamond crossover
superimposed pair of railway crossovers, resembling a letter X, permitting to travel in either direction between a pair of parallel tracks
diamond crossover: X-shaped track junction for four-way rail movement
A diamond crossover is a grade-separated or at-grade track junction formed by two standard crossovers (turnouts) arranged in an X pattern. It allows trains to move in either direction between two parallel tracks without conflicting with other movements, unlike a simple crossover which restricts directional flow. The configuration earned its name from the diamond shape formed when viewed from above, though the actual geometry is more precisely two crossing diagonal paths.
The device consists of four switch assemblies and connecting curved or angled rail sections. When aligned for leftbound movement, a train entering from track A can cross to track B and continue left; simultaneously, a train from track C can cross to track D and continue left. The switch positions reverse for rightbound traffic, allowing the same four movements in the opposite direction. This is distinct from a simple crossover, which permits movement in only two directions (typically between parallel tracks in one plane).
Applications and constraints
Diamond crossovers are standard in marshalling yards, passenger terminals, and multi-track trunk lines where frequent interchange between parallel tracks is required. They are more complex and costly to install and maintain than simple crossovers, requiring more extensive foundation work and precise alignment. Track gauge, rail weight, and the distance between the parallel tracks determine the minimum and maximum angles of the diagonals; steeper angles reduce land footprint but increase wear and limit train speed through the junction.
Fouling occurs if a train occupies one diagonal while another attempts to use the crossing path, so interlocking logic and signalling must prevent simultaneous conflicting movements. On high-speed lines or where trains frequently traverse the junction, diamond crossovers with small crossing angles (6 degrees or less) are preferred to reduce impact forces and wheel wear. Maintenance challenges include differential settlement of the four separate track beds and the high stresses concentrated at the crossing point.