A one-way pair, one-way couple, or couplet refers to that portion of a bi-directional traffic facilitysuch as a road, bus, streetcar, or light rail linewhere its opposing flows exist as two independent and roughly parallel facilities. Description In the context of roads, a one-way pair consists of two one-way streets whose flows combine on one or both ends into a single two-way street. The one-way streets may be separated by just a single block, such as in a grid network, or may be spaced further apart with intermediate parallel roads. One use of a one-way pair is to increase the vehicular capacity of a major route through a developed area such as a central business district. If not carefully treated with other traffic calming features, the benefit in vehicular capacity is offset by a potential for increased road user deaths, in particular people walking and biking. A one-way pair can be created by converting segments of two-way streets into one-way streets, which allows lanes to be added without widening. On occasion, "couplet" has been applied specifically to the point where the one-way streets and the two-way street meet, rather than the paired one-way streets themselves. Flows on a one-way pair may follow the traffic handedness convention of the locale, or may be switched. Following the convention allows a one-way pair to be more easily integrated into an existing network of two-way streets, as a single two-way street is effectively split into the two sides of the pair, as in the diagram below: Examples Australia Sydney CBD features a number of one way pairs, all north-south. One example is Pitt Street with Castlereagh Street. Pitt street carries only northbound traffic from Goulbern Street to Market Street. Castlreagh Street only carries southbound traffic on its entire length from Hunter Street to Hay Street near central station. Trams once ran from Central Station to Circular Quay along Pitt Street and back to Central Station along Castlereigh, Bligh, Bent and Loftus Streets. In Redfern, part of Elizabeth Street is paired with Chalmers street. This follows the usual flow convention. In the Brisbane CBD Ann Street is paired with Turbot Street and George Street with North Quay, the latter by the Brisbane River. In Southbank, Merivale Street is paired with Cordelia Street from Montague Road to Vulture Street. In East Brisbane, Vulture Street is paired with Stanley Street. Japan Japan National Route 340 travels through