page_title: Grand union
section_title: Three-quarter, half and butterfly unions
hierarchical_section_title: Grand union / Three-quarter, half and butterfly unions
caption_attribution_description: English: Cross junction in the northwest corner of the Loop in Chicago. Русский: Перекрёсток в северо-западном углу «петли» в Чикагском метрополитене.
context_page_description: A grand union is a rail track junction where two double-track railway lines cross at grade, often in a street intersection or crossroads. A total of sixteen railroad switches allow streetcars coming from any direction to take any of the three other directions. The same effect may be achieved with two adjacent wyes if the location allows for space.
context_section_description: Three-quarter unions are similar to grand unions in that they are also rail track junctions where two double-track railway lines cross at grade, often in a street intersection or crossroads; the primary difference being that one corner of the crossing does not have curved junction tracks, with the union having a total of 12 railroad switches (sets of points).
  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.
caption: Chicago Transit Authority control tower 18 at this three-quarter union guides elevated Chicago 'L' north and southbound Purple and Brown lines intersecting with east and westbound Pink and Green lines and the looping Orange line above the Wells and Lake street intersection in the Loop.
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