Contraflow lane

In transport engineering nomenclature, 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, part of the southbound HOV lane on I-5 between Seattle and Tacoma is a contraflow lane on what is otherwise the northbound side of the highway.

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 mi 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.

Bicycle contraflow lanes


Contraflow is a common part of decent cycling infrastructure and is often seen on one-way streets. A standard example is that car and other vehicular traffic might have only one lane while on both sides there are bike lanes; one going in the same direction as the vehicular traffic, the other (the contraflow bike lane) allows cyclists to safely go in the opposite direction to the cars. This is allowed as the road may not be wide enough for two lanes of car traffic but there is enough room to allow for the additional bicycle lane; and without it cyclists may be forced to take a long, and perhaps unsafe, detour.

Another example is the same as the above but there is only one bike lane, the contraflow lane, and bicycles travelling in the same direction as the cars share the cars' lane. This solution would be more suited to very narrow roads or ones with light traffic.

Contraflow cycling is often assumed to be associated with higher accidents risks, but where it has been properly evaluated, contraflow cycling actually seems to reduce the accidents risk.