Contra-flow

In transport engineering , a counterflow lane or contraflow lane is a lane in which traffic flows in the opposite direction of the surrounding lanes.

Contraflow lanes are often used for bicycles or bus rapid transit on what are otherwise one-way streets. In a sample configuration for buses, a street might have four lanes: the outermost lanes are reserved for buses in both directions, while the center two lanes are available for general traffic in only one direction. Thus, the street functions as two-way for buses, but one-way for all other vehicles.

Contraflow lanes can also be used to extend the capacity of separated limited-access roads when there are physical constraints. For example, the Boston I-93-Southeast Expressway "Zipper-Lane", which provides an HOV lane for the morning rush on the northbound side, and the afternoon rush on the southbound side.

In certain situations, reversible lanes will be contraflow for a portion of the day. The Lincoln Tunnel XBL to the Lincoln Tunnel is a contraflow exclusive bus lane for buses during the morning peak period. The XBL lane is fed by the New Jersey Turnpike at Exits 16E and 17, and New Jersey Route 3. The helix, tunnel, and terminal are owned and operated by the Port Authority of New York and New Jersey, the bi-state agency that also operates the 2.5-mile (4.02 km) contraflow lane along the left lane of three westbound lanes. The XBL serves over 1,800 buses, which transport more than 65,000 persons, each morning and is a major component of the morning "inbound" commutation crossing the Hudson River.

When lanes on motorways are closed for repair and maintenance, a contraflow lane may be set up on the other side of the central reservation.

Contraflow bus lanes, areas in which a dedicated lane of an otherwise one way street is reversed for buses and other mass transit, exist in locations such as:

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