Reversible lane

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The Lions Gate Bridge from the south end in Stanley Park, Vancouver.
The Lions Gate Bridge from the south end in Stanley Park, Vancouver.

A reversible lane (counterflow lane, or contraflow lane in transportation 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. Some people refer to non-physically-separated reversible lanes as suicide lanes due to many fatal accidents occurring when drivers failed to pay attention to the lights and lane markings and got into head-on collisions.

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 it to maintain orderly flow of traffic.

Contents

[edit] Signals and Markings

Example of signals in Edmonton, Alberta.
Example of signals in Edmonton, Alberta.

In the US, 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, becoming solid yellow before turning red. Other setups had double-turn-lane signs backlighted 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.

[edit] Separation of Flows

Some more recent implementations of reversible lanes use a moveable 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.

[edit] Passing lanes

Typical striping on an old-style suicide lane setup in the United States.
Typical striping on an old-style suicide lane setup in the United States.
Markings for reversible lanes in Sweden.
Markings for reversible lanes in Sweden.

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.

[edit] Turn lanes

This is a typical 5-lane arterial equipped with a center-turn lane. These are often found in cities, towns and developed areas near cities. In the United States, the broken line is located on the inside of the lane. In Canada (except British Columbia), the broken line is located on the outside.
This is a typical 5-lane arterial equipped with a center-turn lane. These are often found in cities, towns and developed areas near cities. In the United States, the broken line is located on the inside of the lane. In Canada (except British Columbia), the broken line is located on the outside.

Another type of center two-way lane is a center left-turn lane (for countries which drive on the right) or just center 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.

[edit] Examples

[edit] No (or minimal) lane controls

[edit] Lane controls and no (or minimal) physical separation

Trans-national

  • The Peace Bridge between the US 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 . Approach works commenced in Jan 2007 for a second bridge over the Georges River at a cost of $45 million AUD, eliminating the need for a reversible lane. However, a 300m long reversible centre lane will still remain on Alfords Point Road over Henry Lawson Drive, approximately 500 metres 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.
  • Tasmania Bridge, Hobart, Tasmania. 5 lanes total, with center lane reversible

Canada


United Kingdom

  • 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 A38(M) Aston Expressway, Birmingham, England (7 lanes total, 3 reversible: allowing for either 4 out, 2 in, 1 buffer, or 2 out, 4 in, 1 buffer).

United States

  • The Golden Gate Bridge (6 lanes total, 2 reversible, vertical median markers provide minimal physical separation)
  • West Alabama Street and North Main Street in Houston, Texas - 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.
  • There is at least one road in Sandusky, Ohio that has reversible lanes, for the purpose of allowing quick departure of Cedar Point guests.
  • Baxter Avenue and Bardstown Road (U.S. Highway 31E) in Louisville, Kentucky 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.
  • Nicholasville Road (U.S. Highway 27) in Lexington, Kentucky 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.
  • The Chesapeake Bay Bridge near Annapolis, Maryland (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.
  • Asylum Avenue in Hartford, Connecticut
  • In Dallas, Texas, 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 the center. 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.
  • The Clay Wade Bailey Bridge in Covington, Kentucky (3 lanes total, 1 reversible)
  • 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.
  • The access road to Artificial Island (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.

[edit] Lane controls and physical separation by empty lane

[edit] Lane controls and physical separation by movable barrier

[edit] Third (reversible) carriageways on freeways

See also: Express lanes

[edit] Entire roadway routinely reversed

South and Marion Roads provide access to the Southern Expressway at its northern end. Here, southbound access to the expressway from South Road is restricted.
South and Marion Roads provide access to the Southern Expressway at its northern end. Here, southbound access to the expressway from South Road is restricted.
  • 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 worlds 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.
  • Rock Creek and Potomac Parkway in Washington, D.C. Four lanes, all reversible, all flowing in the direction of prevailing traffic during rush hour each day.
  • 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 day.
  • 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.

[edit] Oddities

  • Ontario provincial highway 17 has a railroad on the north side in Sault Ste. Marie, Ontario; the center lane on this corridor is restricted to westbound traffic. A double-yellow solid line separates the eastbound through lanes and the center lane. However, that corridor will lose its "Highway 17" status in favor of a freeway construction project that will relocate traffic to the freeway north of the railroad when construction is completed in 2008.

[edit] See also

[edit] External links

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