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Intersection (road)

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An intersection, also known as an at-grade junction, is a place where two or more roads meet, cross, or diverge. These junctions occur at the same height, meaning the roads exist on the same level. This is a key distinction from an interchange. An interchange uses bridges or tunnels to separate different roads so they do not touch. Intersections are essential for navigation. They allow travelers to transition between different streets and directions.

Street intersection diagram
Street intersection diagram

Intersections are often classified by the number of road segments, or arms, that connect to them. A three-way intersection might take the form of a T-junction or a Y-junction. A Y-junction is sometimes called a fork if you approach it from the stem.

Fork in the road
Fork in the road

A four-way intersection is commonly called a crossroads. In these spots, two streets usually cross each other. They might meet at a perpendicular angle, or they might cross at a different angle entirely. Some junctions are offset, meaning the ends of the roads do not line up perfectly. While four-way junctions are common, some places have six-way intersections. These occur when three streets cross at one single point.

Veterans Memorial Parkway, London, Ontario
Veterans Memorial Parkway, London, Ontario

Even more complex junctions, such as those with seven or more approaches, are quite rare.

Makati intersection
Makati intersection

To manage the movement of vehicles, engineers use various traffic controls. Uncontrolled intersections have no signs or signals to guide drivers. In these cases, priority rules, or right-of-way rules, determine who moves first. For example, at a four-way intersection, traffic from the right often has priority. Yield-controlled intersections use "yield" or "give way" signs to tell drivers when to slow down or stop. Stop-controlled intersections use "STOP" signs to manage the flow. Some locations use signal-controlled intersections, which rely on electric traffic lights. These lights indicate which direction is allowed to proceed at a specific time.

Right turn on red Belgrade, Serbia
Right turn on red Belgrade, Serbia

Lane design is another way to organize an intersection. A traffic circle directs traffic streams around a circular path. These can take many forms, such as roundabouts, rotaries, or mini-roundabouts. Some intersections also use turn lanes, which are also called turn bays. These lanes allow vehicles to cross oncoming traffic or exit a road without blocking others. Turn lanes are vital for safety and capacity. In rural areas, adding left turn lanes at stop-controlled intersections can reduce crashes by up to 48%. At signalized intersections, these lanes can reduce crashes by 33%.

Street intersection diagram
Street intersection diagram

Engineers also develop unconventional intersection configurations to improve traffic throughput. These designs aim to manage turning traffic more efficiently. One example is the Michigan left, which combines a right turn with a U-turn. Another is the jughandle left, where drivers diverge to the right before curving left. Other complex designs include continuous-flow intersections, superstreets, and Texas U-turns. The Federal Highway Administration also promotes the Diverging Diamond Interchange as part of an initiative started in 2012. These methods help reduce delays and increase the number of vehicles that can pass through a junction safely.

Intersections must also protect vulnerable road users. This group includes pedestrians, cyclists, motorcyclists, and people on motorized scooters. These users are at a higher risk of serious injury compared to people in cars.

1 times square night 2013
1 times square night 2013

To assist them, cities use pedestrian aids like crosswalks and "walk" signals. Some intersections use a pedestrian scramble. This is an all-way stop for vehicles that allows pedestrians to cross in any direction, including diagonally. The crossing at Shibuya Station in Tokyo is a famous example of this. In the United States, more than 50% of pedestrian deaths in 2020 were attributed to failure to yield the right of way, which often happens at intersections.

1 times square night 2013
1 times square night 2013

Finally, intersections connect to many different aspects of our infrastructure. They are central to urban planning and civil engineering. They also play a role in environmental management, as larger turn lanes can increase stormwater runoff. In some cases, they even intersect with railways. An at-grade railway crossing is one where the tracks cross a road without using an embankment or a cut. This requires specialized level crossings to ensure safety for both drivers and trains.

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🖼️ Images & Media (9)
File:Площадь Тверская Застава (вид сверху).jpg
Площадь Тверская Застава (вид сверху).jpg
File:Makati intersection.jpg
Makati intersection.jpg
File:Bonneuil 16 Carrefour Bellevue 2012.jpg
Bonneuil 16 Carrefour Bellevue 2012.jpg
File:Fork in the road.jpg
Fork in the road.jpg
File:Veterans Memorial Parkway, London, Ontario.jpg
Veterans Memorial Parkway, London, Ontario.jpg
File:Right turn on red Belgrade, Serbia.JPG
Right turn on red Belgrade, Serbia.JPG
File:Street intersection diagram.svg
Street intersection diagram.svg
File:1 times square night 2013.jpg
1 times square night 2013.jpg
File:Crossroads sign in Clarksdale, Mississippi.jpg
Crossroads sign in Clarksdale, Mississippi.jpg
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