Grand union

A grand union is a rail track junction where two double-track railway or tramway lines cross at grade, often in a street intersection or crossroads.

Special parts, sometimes made of manganese steel, are needed for each location where one rail crossed another (a "frog"); these parts often need to be custom-made and fitted for each single location, depending on the specific angle of crossing of the intersecting streets.

In an intersection with lines oriented towards cardinal directions, these could be: north-south, north-east, north-west, south-east, south-west, and east–west.

Half unions are similar, but have curved junction tracks on only two adjoining corners of the intersection, with a total of eight switches.

Butterfly unions share the total of eight switches, but the curved junction tracks are on opposing corners.