cross junction
A location where two railroad tracks cross, without switches, as where different roads intersect.
cross junction: where two rails cross at grade without merging
A cross junction is a point where two railroad lines intersect at the same level, with tracks crossing one another at an angle (typically 90 degrees, though acute angles occur). Unlike a conventional switch or turnout, there is no mechanism to divert traffic from one line to another. A train on either track passes straight through the intersection; the rails of both lines occupy the same physical space only at the crossing point itself.
The geometric challenge at a cross junction is severe. At the instant a wheel flange from one line would contact a rail of the crossing line, a diamond-shaped closure must exist. This is achieved by the crossing itself, a fabricated unit where four rails meet. The flange ways (channels in the rails that guide and support wheel flanges) are interrupted at the crossing, leaving a small gap or open segment where wheels must bridge unsupported for a few inches. The exact width and geometry of this gap is critical; if too wide, a wheel flange may drop into it and derail.
Cross junctions appear where two independent rail operators' lines must cross without operational connection, or at grade separations where geography or cost prohibits a bridge. They are common at busy urban rail nodes where multiple companies' routes intersect. Unlike a junction with switches, a cross junction adds minimal capacity for routing flexibility but imposes no speed restriction if properly maintained. Trains crossing at speed may experience a jarring transition as the wheel moves from one rail profile to the crossing unit and back.
Maintenance is intensive. The diamond crossing unit must be installed to high precision and checked regularly for wear, settlement, and damage from impact loads. The flangeways must be kept clear of debris and ice in winter. A worn or misaligned crossing generates noise, accelerates wheel and rail damage, and poses a derailment risk. Replacement of a diamond crossing is expensive and often requires temporary single-track operation or speed restrictions during installation.
In modern rail terminology, a cross junction is distinct from a grade separation (which uses a bridge or underpass) and from a switched junction (which uses turnouts). Some engineers refer to the crossing unit itself as the diamond because of its four-pointed shape when viewed from above. On heritage railways and heavily trafficked urban lines, the smooth passage of trains over a worn crossing is a matter of both schedule and safety.