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Reversible lane
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A reversible lane (called a counterflow lane or contraflow lane in transport engineering nomenclature) is a lane in which traffic may travel in either direction, depending on certain conditions. Typically, it is meant to improve traffic flow during rush hours, by having overhead traffic lights and lighted street signs notify drivers which lanes are open or closed to driving or turning.
Reversible lanes are also commonly found in tunnels and on bridges, and on the surrounding roadways — even where the lanes aren't regularly reversed to handle normal changes in traffic flow.
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Encyclopedia
A reversible lane (called a counterflow lane or contraflow lane in transport engineering nomenclature) is a lane in which traffic may travel in either direction, depending on certain conditions. Typically, it is meant to improve traffic flow during rush hours, by having overhead traffic lights and lighted street signs notify drivers which lanes are open or closed to driving or turning.
Reversible lanes are also commonly found in tunnels and on bridges, and on the surrounding roadways — even where the lanes aren't regularly reversed to handle normal changes in traffic flow. The presence of lane controls allows authorities to close or reverse lanes when unusual circumstances (such as construction or a traffic accident) require use of fewer or more lanes to maintain orderly flow of traffic.
Signals and markings
In the United States, reversible lane markings are typically a dashed or broken double yellow line on both sides. Most often done on three-lane roads, the reversible lane is typically used for traffic in one direction at morning rush hour, the opposite direction in the afternoon or evening, and as a turning lane at most other times. There is also a transition period (typically 30–60 minutes) between reversals prohibiting traffic of any kind in the reversing lane, in order to prevent collisions. Sometimes, lane control signals are placed over the roadway at regular intervals (within sight of each other) indicating which lanes are allocated to which travel direction; a red X indicates the lane is closed or reserved for the opposite direction; a green arrow indicates a permitted travel lane. The center lane is marked with either one of those (depending on time of day), and often a flashing yellow X at other times to indicate an imminent closure of a lane, becoming solid yellow before turning red. Other setups had double-turn-lane signs backlit with white fluorescent lighting instead of the flashing yellow X.
Other streets with reversible lanes (including several in Washington, D.C.) simply have signs posted indicating what lanes are open to which direction when.
Separation of flows
Some more recent implementations of reversible lanes use a movable barrier to establish a physical separation between allowed and disallowed lanes of travel. In some systems, a concrete barrier is moved during low-traffic periods to switch a central lane from one side of the road to another; some examples are the Coronado Bridge in San Diego, California, the seven lane Tappan Zee Bridge on the Hudson River in New York and the 8 lane Auckland Harbour Bridge across the Waitemata Harbour in Auckland, New Zealand. Other systems use retractable cones or bollards which are built into the road, or retractable fences which can divert traffic from a reversible ramp. The two center lanes of the six-lane Golden Gate Bridge are reversible; they are southbound during morning rush hour and northbound at evening rush hour, and are demarcated by vertical yellow markers placed manually in sockets in the roadway.
Many urban freeways have entirely separate carriageways (and connecting ramps) to hold reversible lanes (the reversible lanes in such a configuration are often referred to as "express lanes"). Generally, traffic flows in one direction or another in such a configuration (or not at all); the carriageways are not "split" into two-lane roadways during non-rush periods. Typically, this sort of express lane will have fewer interchanges than the primary lanes, and many such roadways only provide onramps for inbound traffic, and offramps for outbound traffic.
Passing lanes
Historically, a "suicide lane" has also referred to a lane in the center of a highway meant for passing in both directions. Neither direction had the right-of-way, and both directions were permitted to use the lane for passing. Head-on accidents were common. Very few of these setups are left (at least in the United States ), though sometimes a similar layout exists, where three lanes are striped with two in one direction and one in the other, but traffic in the direction with one lane is allowed to cross the centerline to pass. However, this is not as dangerous, because one direction has clear right-of-way. They still however have 2-lane roads with 4-lane right-of-way where only the oncoming traffic in the opposite lane has to be checked as opposed to risking in a center lane.
Turn lanes
Another type of center two-way lane is a center left-turn lane (for countries which drive on the right), center turn lane or median turn lane, a single lane in the center of the road into which traffic from both directions pulls to make a left turn. It is also used by drivers turning left onto the main road. While this is sometimes also called a "suicide lane", it is actually far safer, as car accidents occur at far lower speeds.
These roads are very common in suburban areas, and rather less common in rural areas. Many were divided highways before the median was demolished or otherwise filled with the turn lane.
This center lane can be used by emergency vehicles like police cars, ambulance, and fire trucks to avoid traffic travelling in either direction. Drivers are never allowed to use the center lane of such a highway for passing slow-moving vehicles.
Examples
No (or minimal) lane controls
Lane controls and no (or minimal) physical separation
Trans-national
- The Peace Bridge between the U.S. and Canada, connecting Fort Erie, Ontario to Buffalo, New York. 3 lanes total, all marked reversible, 1 reversed in the direction of rush hour flow with the possibility of all lanes flowing in the same direction based on traffic needs.
- The Lewiston-Queenston Bridge connecting Niagara-on-the-Lake, Ontario to Lewiston, New York. 5 lanes total, all marked as reversible, 1 to 4 lanes marked daily in the same direction depending on traffic needs. In addition to the directional signals, special signals are also fitted to specify what type of vehicle may use the lane.
Australia
- The Sydney Harbour Bridge in Sydney, New South Wales (8 lanes total, 3 (formerly 4) potentially reversible, 3 reversed daily. AM peak 6 South 2 North. PM peak 3 South 5 North. Other times, 4 South 4 North),
- The Spit Bridge, Sydney, New South Wales (4 lanes total. AM peak 3 South, 1 North. PM peak 3 North, 1 South. All other times 2 North, 2 South).
- The Alfords Point Bridge in the south-western suburbs of Sydney, New South Wales. 3 lanes total, with the centre lane reversible using manual placement of plastic bollards. Originally this bridge was built with two lanes, and was to be part of twin spans, but only the foundations and excavations for approach works were built for the Eastern span, and the bridge was opened with one lane used in each direction. New approach works commenced in January 2007 for the second span, at a cost of $45 million AUD, eliminating the need for a reversible lane. However, a 300-meter reversible centre lane will still remain on Alfords Point Road over Henry Lawson Drive, approximately 500 meters north of this proposed bridge.
- Flagstaff Road in the southern suburbs of Adelaide, South Australia. 3 lanes total, with the centre lane reversible.
- Johnston Street, Melbourne, Victoria. 5 lanes total, with the centre lane reversible.
- Queens Road, Melbourne, Victoria. 5 lanes total, with the centre lane reversible.
- Coronation Drive, Brisbane, Queensland.
- Tasman Bridge, Hobart, Tasmania. 5 lanes total, with center lane reversible
Canada
- The Lions' Gate Bridge in Vancouver (3 lanes total, 1 reversible)
- The Pitt River Bridge in Pitt Meadows
- The Angus L. Macdonald Bridge, Chebucto Road and the Herring Cove Road in Halifax, Nova Scotia (3 lanes total, 1 reversible)
- Jarvis St. in downtown Toronto (5 lanes total, centre lane reversed daily for AM/PM rush hours)
- Okanagan Lake Bridge in Kelowna, British Columbia (3 lanes total, 1 reversible)
- The Champlain Bridge in Ottawa, Ontario (3 lanes total; 1 reversible).
- Sherman Access and Sherman Cut in Hamilton, Ontario (2 lanes, both reversible).
- The George Massey Tunnel in Delta, BC and Richmond, BC (4 lanes total, 2 reversible, with access controlled by gates).
- Connors Road amongst other roads that enter into the river valley in Edmonton, Alberta. (4 lanes, 3 reversible).
- 170 St in Edmonton, Alberta north of 137 Ave (3 lanes, 1 reversible).
- 97 St in Edmonton, Alberta (5 lanes, 1 reversible).
- Centre Street from 16th Avenue North to 6th Avenue South in Calgary, Alberta. (4 lanes total, 2 reversible; standard configuration is 2 out, 2 in; morning rush is 1 out, 3 in; and evening rush is 3 out, 1 in.)
- 10th Street North / 9th Street South from 5th Avenue North to 4th Avenue South in Calgary, Alberta. (4 lanes total, 2 reversible; standard configuration is 2 out, 2 in; morning rush is 1 out, 3 in; and evening rush is 3 out, 1 in.)
- Park Avenue in Montreal, Quebec, five lanes total, centremost lane is reversible, sidemost lanes are reserved for public transport during rush hour. Morning rush is 2 in, one out (not including bus lanes), evening rush is reversed.
- Champlain Bridge (Montreal), rush hour bus lanes
- Jacques Cartier Bridge (Montreal), five lanes total, two for both directions, one rush hour central reversible lane
Croatia
- State Route 102 near Kraljevica leading southbound to the Krk Bridge used to have a three-lane passing lane combination, blind curves, and a steep grade. It was later changed to a passing lane combination that makes the northbound traffic dominant.
Turkey
- Reversible lanes are frequently used in hilly sections of interstate roads with heavy truck traffic. Most of them were built during the 1980s and 1990s.
United Kingdom
- The A38(M) Aston Express Way in Birmingham, England. Constructed in 1971, it was the United Kingdom's first contraflow road. It is 2 miles long.
- The A61 Queens Road in Sheffield, England, although it is a very short section (4 lanes total, 1 reversible: allowing for either 3 out, 1 in, or 2 out, 2 in).
- The A470 North Road in Cardiff, Wales, A section of around 1 mile long between the Maindy Road Junction and College Avenue where the road drops from a dual two-lane to a three-lane section. One lane is always dedicated to Northbound (out of town) traffic, and one lane to Southbound (city centre bound traffic) with the centre lane reversing depending on the time of day - i.e. in the morning 2 lanes into the city, 1 lane out, in the evening 2 lanes out of the city, 1 lane in.
- The A15 in Lincoln (Canwick Road) has a short three-lane section of tidal flow.
United States
Alabama
- In Montgomery, Norman Bridge Road through the Garden District and Old Cloverdale has a center lane with reversible markings and traffic flow lights between Burton Street and Legrand Place.
Arizona
- In Phoenix on 7th Avenue between McDowell Road and Northern Avenue, and 7th Street between McDowell Road and Cave Creek Road/Dunlap Avenue. On both roads, the lane configuration is 2 southbound and 3 northbound, with the center lane open for southbound traffic between 6-9am and open to northbound traffic between 3-6pm. No left turns are permitted during these hours for either direction.
California
- The Golden Gate Bridge (6 lanes total, 2 reversible, vertical median markers provide minimal physical separation) connecting San Francisco with suburban Marin County
- Doyle Drive (U.S. Route 101) in San Francisco
- Lafayette Street in Santa Clara - the center lane is used for northbound traffic on weekday mornings, southbound traffic for weekday afternoons, and as a center turning lane at other times.
Connecticut
Georgia
- Vineville Avenue in Macon: the center lane of three is reversed using overhead lane-use control signals.
Kentucky
- The Clay Wade Bailey Bridge in Covington (3 lanes total, 1 reversible)
- Nicholasville Road (U.S. Highway 27) in Lexington, has reversible lanes (lane signals, no physical separation) starting at its intersection with Rose Street at the University of Kentucky campus and ending at New Circle Road, the city's inner beltway. During morning rush hour, southbound traffic (away from the UK campus and downtown) is restricted to one lane between campus and Southland Drive, and two lanes from Southland to New Circle. Northbound traffic faces the same restrictions in the evening rush hour. During off-peak hours, an equal number of lanes are dedicated to traffic in each direction.
- Baxter Avenue and Bardstown Road (U.S. Highway 31E) in Louisville have reversible lanes (lane signals without any physical separation) for 2½ miles starting at their intersection with Lexington Road and ending at Douglass Boulevard. Southbound traffic leaving downtown Louisville is restricted to one lane during the morning rush hour, with northbound traffic having the same restriction during the evening rush hour. Electronic signs over the roadway alert motorists to the traffic flow dedication of each lane.
Indiana
- In Indianapolis, Fall Creek Parkway North Drive between Central Avenue and Evanston Avenue has 5 lanes (7 in some sections) with 1 lane marked as reversible. Configuration is typically designed to allow for 3 in 2 out during morning rush hours, and 2 in/3 out during afternoon rush hours. Due to Fall Creek Parkway's proximity to the Indiana State Fairgrounds, lane configurations change periodically to facilitate traffic flow during events at the fairgrounds.
Maryland
- The Chesapeake Bay Bridge near Annapolis (5 lanes total, all marked reversible, 1 usually reversed for normal peak traffic). However, due to its dual spans, when there are 2 eastbound lanes and 3 westbound the opposing sides are completely divided, this is the usual configuration.
- The Hanover Street Bridge in Baltimore has 5 lanes total marked reversible, with 1 usually reversed for normal peak traffic).
- Georgia Avenue in Silver Spring has 7 lanes. During most hours, the center lane is marked with a yellow lit X as a left turn lane for both directions. During morning and evening rush hours, the lane is marked with a down facing green arrow – southbound in the morning, northbound in the evening – or a red X – northbound in the morning, southbound in the evening – and left turns are prohibited.
- Colesville Road in Silver Spring has 6 lanes. During off-rush hours, three lanes go in each direction. During morning rush hours, four lanes (marked with green arrows) go southbound, while northbound (marked with Xs in those lanes) is relegated to two lanes. During afternoon rush, the process is reversed.
Nebraska
- A portion of Dodge Street west of downtown Omaha: no physical separation; lanes marked with overhead lane-use control signals.
New Jersey
- The access road to Artificial Island in Lower Alloways Creek Township (home of both Hope Creek Nuclear Generating Station and Salem Nuclear), Alloway Creek Neck Road, has three lanes total. The lanes can be switched direction with overhead signage for either the shift change, auto accidents, or made completely one-way in either direction, depending on the circumstances.
New York
- Delancey Street in New York City has two lanes on the eastbound side adjacent to the median used for westbound traffic in the morning rush hour between the Williamsburg Bridge and Allen Street. All traffic in these lanes must continue to and then turn left onto Allen, during these times left turns are prohibited from the regular westbound roadway onto Allen Street.
- Manhattan Bridge (New York City) lower level has three lanes, which can have all lanes used in one direction or reversible with two lanes one way and the other for the opposite direction.
- The upper level of the Queensboro Bridge in New York City has 4 lanes and can have all flowing outbound (PM peak), or two lanes each direction in normal configuration.
North Carolina
Ohio
- At least one road in Sandusky has reversible lanes, for the purpose of allowing quick departure of Cedar Point guests.
Pennsylvania
- The Liberty Bridge near the southern terminus of I-579 in Pittsburgh has 4 lanes, all of which are potentially reversible, and 2 of which are reversed based on rush-hour times.
Texas
- In Dallas, two of the major streets leading into downtown (Ross Avenue and Live Oak Street) have five lanes with three different lane configurations. During morning rush hour, three lanes go inbound to downtown, with one lane going outbound and a turn-only lane in between. During evening rush hour, three lanes go outbound, still with the center turn-only lane. All other times, the streets are configured for two inbound lanes and two outbound lanes with a turn-only lane in the center.
- West Alabama Street and North Main Street in Houston – both are three-lane streets, which operate in a 2 in 1 out configuration during the morning rush, a 1 in 2 out configuration during the evening rush, and a 1 each way + two-way left turn lane at other times.
Lane controls and physical separation by empty lane
- The A38(M) motorway (otherwise known as the Aston Expressway) in Birmingham, England. The road heads out of the city centre towards Spaghetti Junction on the M6. It is a 7 lane section of motorway with no central reservation, while one lane remains closed to traffic. Overhead lane control signals allow for 4 lanes in, 2 out in the morning rush hour, vice versa in the evening, and 3 lanes either way at other times.
- The U.S. Route 78 portion in Snellville, GA, United States, has 6 lanes in total. This occurs from the limited access portion through Stone Mountain Park to G.A. State Route 124 (Scenic Highway) for several miles. The middle two lanes are reversible (usually occurring during rush hour) with a varying lane always reserved a center turn lane while the 3 lanes are used for one side and 2 for the other.
- The Caldecott Tunnel between Oakland, California and Contra Costa County, California has three separate bores, with the middle bore switching direction twice daily for rush hour traffic.
Lane controls and physical separation by movable barrier
Third (reversible) carriageways on freeways
- Bundesautobahn 7, New Elbe Tunnel, Hamburg, Germany (actually two reversible carriageways, plus two fixed)
- Warringah Expressway in Sydney, Australia
- Interstate 5 in Seattle, Washington, and Interstate 90 from Bellevue to Seattle, Washington
- Interstate 15 in northern San Diego, California
- Interstate 25 and US-36 in Denver, Colorado
- Interstate 394 through Minneapolis, Minnesota and its western suburbs
- Interstate 90/Interstate 94 (Kennedy Expressway portion) in Chicago, Illinois
- Interstate 70 through St. Louis, Missouri
- Lee Roy Selmon Crosstown Expressway from Brandon to Tampa, Florida
- Interstate 64 in Norfolk, Virginia (center carriageway reserved for HOV traffic during rush hour)
- Interstate 395 and Interstate 95 through Washington, D.C. and its Virginia suburbs (center carriageway reserved for HOV traffic during rush hour)
- Lincoln Tunnel between Weehawken, New Jersey and New York, New York has three tubes with two lanes each. The center tube carries two lanes in peak direction weekdays (with a reserved inbound bus lane during the AM rush period) and a single lane each direction off-peak (nights, weekends, holidays).
- Interstate 93 through Boston, Massachusetts
Entire roadway routinely reversed
* The Anchieta/Imigrantes highway system in Brazil contains the world's longest fully reversible road (The Imigrantes variant at a length of 58.5 km). It comprises a total of 10 lanes distributed over 4 separate roadways (3+3+2+2), each of which can be reversed. Traffic flow is unidirectional on up to three roadways at a time, in different combinations, depending on demand. Since this highway system is the only quick route from São Paulo to the beach, the majority of the traffic on Fridays and Sundays are cars on weekend trips, creating highly asymmetrical demand.
- The Southern Expressway in Adelaide, South Australia is the world's longest exclusively one-way reversible road, spanning 21 km though the city's southern suburbs. It changes direction to carry peak hour traffic to the city centre in the morning and away from the city in the evening. On weekends the directions are reversed.
- In Washington, D.C., the Rock Creek and Potomac Parkway between the Lincoln Memorial and Calvert St. is converted from two lanes in each direction to one-way southbound in the morning and one-way northbound in the evening rush hour Monday through Friday, excluding federal holidays. The P Street exit, usually unavailable northbound, is an allowed left exit in the evening. South of Virginia Avenue, two lanes are closed during rush hours to facilitate the merge to or from Virginia Avenue. There are no overhead markings, but police barricades block wrong-way entrances to the roadway.
- In Washington, D.C., parts of 15th Street NW and 17th Street NW are one-way during certain hours. There are no overhead markings on either road.
- Canal Road in Washington, D.C. (between Foxhall Road and Arizona Avenue)
- Sherman Access in Hamilton, Ontario. 2 lanes total, both marked as reversible, with both lanes flowing in the same direction during rush hour each weekday.
- The lower deck of the Centre Street Bridge in Calgary, Alberta is fully reversible. It normally allows for two way traffic, but both lanes flow in the same direction during rush hour each day.
- Victoria Bridge, in Montreal, Quebec, normally allows for two-way traffic. But during rush hours, it only allows one-way traffic, northbound in the morning, and southbound in the afternoon.
See also
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