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A three-way junction (or three-way intersection) is a type of
*In some jurisdictions, chiefly in European countries except the U.K. and Ireland, a driver is always obliged to yield right-of-way for every vehicle oncoming from the right at a junction without traffic signals and priority signs (including T junctions). *In other jurisdictions (mainly in the U.K., USA, Australia and
File:Taiwan road sign Art030.2.svg, T Intersection Sign in Taiwan with no more road straight ahead
File:Taiwan road sign Art030.3.png, T Intersection Sign in Taiwan with side road on the left
File:Taiwan road sign Art030.4.png, T Intersection Sign in Taiwan with side road on the right
File:Taiwan road sign Art030.7.png, Y Intersection Sign in Taiwan
File:Taiwan road sign Art030.8.png, 3-way Intersection Sign in Taiwan with side road on the right but not right angle
File:Taiwan road sign Art030.9.png, 3-way Intersection Sign in Taiwan with side road on the left but not right angle
A three-way junction (or three-way intersection) is a type of road intersection
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 ...
with three arms. A Y junction (or Y intersection) generally has three arms of equal size coming at an acute
Acute may refer to:
Science and technology
* Acute angle
** Acute triangle
** Acute, a leaf shape in the glossary of leaf morphology
* Acute (medicine), a disease that it is of short duration and of recent onset.
** Acute toxicity, the adverse ef ...
or obtuse angle
In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle.
Angles formed by two rays lie in the plane that contains the rays. Angles ...
to each other; while a T junction (or T intersection) also has three arms, but one of the arms is generally a smaller road joining a larger road at right angle
In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or radians corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. Th ...
.
Right-of-way
Some three-way junctions are controlled bytraffic light
Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control flows of traffic.
Traffic light ...
s, while others rely upon drivers to obey right-of-way
Right of way is the legal right, established by grant from a landowner or long usage (i.e. by prescription), to pass along a specific route through property belonging to another.
A similar ''right of access'' also exists on land held by a gov ...
rules, which vary from place to place:*In some jurisdictions, chiefly in European countries except the U.K. and Ireland, a driver is always obliged to yield right-of-way for every vehicle oncoming from the right at a junction without traffic signals and priority signs (including T junctions). *In other jurisdictions (mainly in the U.K., USA, Australia and
Taiwan
Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the no ...
), a driver turning in a three-way junction must yield for every vehicle approaching the junction (on the way straight ahead) and, if the driver turns right in left-hand traffic/left in right-hand traffic, for every vehicle turning without crossing the oncoming traffic's side of the road (left in left-hand traffic/right in right-hand traffic) ''or'' (if two vehicles both turn right in left-hand traffic) for the right-turning vehicle approaching from the left/(if two vehicles both turn left in right-hand traffic) the left-turning vehicle approaching from the right (and a road going straight ahead at a three-way junction is normally marked as a priority road).
In the United States and some other countries, it is common to have stop signs facing each direction, although according to game-theoretical analysis, drivers have strong incentives to run the stop sign, while randomly removing one stop sign may lead to significant efficiency gains.
In the People's Republic of China, going straight on red when approaching a T junction on the main road with the intersecting road on the left was permitted until the Road Traffic Safety Law of the People's Republic of China took effect on 1 May 2004.
Turns
When one road at a 3-way junction has a higher traffic volume than the other (and particularly when the roads are perpendicular to each other), turns are characterized as "right-in", "right-out", "left-in" and "left-out". A turn "in" represents a turn from the major road into the minor road. A turn "out" represents a turn out of the minor road onto the major road. A 3-way junction allowing all four of these turns is characterized as "full-movement". These terms also apply to turns between roads and driveways.Variations
An experiment was done inIllinois
Illinois ( ) is a state in the Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolitan areas include, Peoria and Rock ...
, United States to allow going straight on red (like a right turn on red
A turn on red is a principle of law permitting vehicles at a traffic light showing a red signal to turn into the direction of traffic nearer to them (almost always after a complete stop, depending on the jurisdiction) when the way is clear, ...
) 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. There are now safer variations of this, called continuous green-T (or seagull) intersections, that have a left turn lane off the main road either channelized or otherwise separated from traffic going straight, which allows for a traffic signal on only one side of the road.An Applied Technology and Traffic Analysis Program ()
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References