A seagull intersection [1] or continuous green T-intersection [2] (also known as a turbo-T [3] (in Florida) or High-T intersection (in Nevada and Utah) [4] [5] ) is a type of three-way road intersection, usually used on high traffic volume roads and dual carriageways. This form of intersection is popular in Australia and New Zealand, and sometimes used in the United States and other countries.
Seagull intersections get their name from the pattern that the two cross-traffic turn lanes make when looking down at them from the air.
In a seagull intersection, one or more lanes of traffic on the arterial road, on the carriageway opposite the intersecting side road, are free flowing, that is, one direction of traffic on the arterial is allowed to travel straight through without stopping. The free-flowing lane(s) are called "continuous green through lane(s)" (CGTL). [6] For the free-flowing through lanes, access into and out of the side road is provided via turn lanes separated from the through lanes in a configuration similar to exit and entrance ramps at an interchange; however, the turn lanes are at the same grade as both carriageways of the arterial and are located on the same side as the oncoming traffic.
Those wishing to turn across traffic into the side road at the intersection drive into the turn lane, which forms one "wing" of the seagull. Here, they meet the opposite carriageway and the side road. Traffic wishing to turn across traffic out of the side road, cross the intersecting carriageway, drive up the other "wing" of the seagull, and merge onto the other carriageway. [7]
For the arterial carriageway adjacent to the side road, access into and out of the side road is ordinarily handled like a conventional T intersection. However, some seagull intersections may have a second, smaller "seagull" formed by two left turning lanes into and out of the side road.
Different methods are used to control traffic where two right-turning movements and the through movement meet. Most intersections use traffic lights, while others use give way (yield) and stop signs, and sometimes roundabouts.
This design type has been proven to provide sustainable benefits when compared the traditional T-intersection design. By reducing delay through the intersection, automobiles use less fuel on average passing through the intersection, and thus emissions are reduced across the intersection. The savings per vehicle may not seem very significant, but when scaled to account for all automobiles passing through the intersection, the total emission savings are significant. Additionally, there are economic and social benefits to reducing delay time and allowing drivers to pass through the intersection quicker. [9] In the Netherlands, this type of intersection occurs by default when a T-junction has a bicycle path on the continuing road, and is not intersected by a roadway for motorized vehicles. The bicycle path may ignore red lights; it is only turning cyclists that must wait for the red light. [10]
An experiment was done[ by whom? ][ when? ] in Illinois, United States to allow going straight on red (following rules analogous to those used for turns on red) when approaching a T junction on the main road, with the intersecting road on the left. It was a failure. However, at some T junctions where the main road includes at least two lanes on the side away from the intersecting road, the farthest (rightmost, in areas where traffic drives to the right) lane is given the right of way to proceed straight through the intersection at all times, denoted by a "green arrow" signal if a traffic light is installed at the intersection. In such cases, often that lane is also specially delimited with pavement markings or other lane separation devices, to keep left-turning traffic on the intersecting road from colliding with traffic proceeding through the intersection on the main road. The seagull intersection was developed as a safer variation of this. [3]
Traffic comprises pedestrians, vehicles, ridden or herded animals, trains, and other conveyances that use public ways (roads/sidewalks) for travel and transportation.
An intersection or an at-grade junction is a junction where two or more roads converge, diverge, meet or cross at the same height, as opposed to an interchange, which uses bridges or tunnels to separate different roads. Major intersections are often delineated by gores and may be classified by road segments, traffic controls and lane design.
A three-way junction is a type of road intersection with three arms. A Y junction generally has three arms of equal size coming at an acute or obtuse angle to each other; while a T junction also has three arms, but one of the arms is generally a smaller road joining a larger road at right angle.
Traffic lights, traffic signals, or stoplights – also known as robots in South Africa, Zambia, and Namibia – are signaling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow of traffic.
A cloverleaf interchange is a two-level interchange in which all turns are handled by slip roads. To go left, vehicles first continue as one road passes over or under the other, then exit right onto a one-way three-fourths loop ramp (270°) and merge onto the intersecting road. The objective of a cloverleaf is to allow two highways to cross without the need for any traffic to be stopped by traffic lights. The limiting factor in the capacity of a cloverleaf interchange is traffic weaving.
A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.
A diamond interchange is a common type of road junction, used where a controlled-access highway crosses a minor road.
A single-point urban interchange, also called a single-point interchange (SPI) or single-point diamond interchange (SPDI), is a type of highway interchange. The design was created in order to help move large volumes of traffic through limited amounts of space efficiently.
A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange.
A hook turn or two-stage turn, also known as a Copenhagen Left, is a road cycling manoeuvre or a motor vehicle traffic-control mechanism in which vehicles that would normally turn from the innermost lane of an intersection instead turn from the outermost lane, across all other lanes of traffic.
A limited-access road, known by various terms worldwide, including limited-access highway, dual-carriageway, expressway, and partial controlled-access highway, is a highway or arterial road for high-speed traffic which has many or most characteristics of a controlled-access highway, including limited or no access to adjacent property, some degree of separation of opposing traffic flow, use of grade separated interchanges to some extent, prohibition of slow modes of transport, such as bicycles, horse-drawn vehicles or ridden horses, or self-propelled agricultural machines; and very few or no intersecting cross-streets or level crossings. The degree of isolation from local traffic allowed varies between countries and regions. The precise definition of these terms varies by jurisdiction.
A continuous flow intersection (CFI), also called a crossover displaced left-turn, is an alternative design for an at-grade road junction. Vehicles attempting to turn across the opposing direction of traffic cross before they enter the intersection. No left turn signal in the intersection is then necessary. Instead, vehicles traveling in both directions can proceed, including through vehicles and those turning right or left, when a generic traffic signal/stop sign permits.
Wanneroo Road is a 44-kilometre (27 mi) arterial highway in the northern suburbs of Perth, Western Australia linking Joondanna and Yokine in the south with Wanneroo and Yanchep in the north. As part of State Route 60, it begins from Charles Street in the inner city and becomes Indian Ocean Drive up to Dongara.
Reid Highway is a 23-kilometre (14 mi) east-west highway and partial freeway in the northern suburbs of Perth, Western Australia, linking North Beach with Middle Swan. As part of State Route 3, it forms half of Perth's outer ring road along with Roe Highway, which it joins onto at its eastern terminus.
A junction is where two or more roads meet.
In traffic engineering, there are regional and national variations in traffic light operation. This may be in the standard traffic light sequence or by the use of special signals.
Springvale Junction is a road intersection in Melbourne, Victoria, Australia. It is situated on the boundary of the suburbs of Mulgrave and Springvale.
Morley Drive is a major east–west road in the inner northern suburbs of Perth, Western Australia, connecting the residential areas of Balcatta, Osborne Park, Tuart Hill, Nollamara, Yokine, Dianella, and Morley with major north-south arterial roads including Wanneroo Road, Alexander Drive, and Tonkin Highway.
A protected intersection or protected junction, also known as a Dutch-style junction, is a type of at-grade road junction in which cyclists and pedestrians are separated from cars. The primary aim of junction protection is to help pedestrians and cyclists be and feel safer at road junctions.
Terminology related to road transport—the transport of passengers or goods on paved routes between places—is diverse, with variation between dialects of English. There may also be regional differences within a single country, and some terms differ based on the side of the road traffic drives on. This glossary is an alphabetical listing of road transport terms.
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