A three-way junction (or three-way intersection) is a type of road intersection with three arms. A Y junction (or Y intersection) generally has three arms of equal size coming at an acute or obtuse angle 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.
Three way junction at Dragons Green - geograph.org.uk - 1578998
Some three-way junctions are controlled by traffic lights, while others rely upon drivers to obey right-of-way 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).[1]
In other jurisdictions (mainly in the U.K., USA,[2] Australia and Taiwan[3]), 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.[4]
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.
Turnsedit
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.[5][6]
Variationsedit
An experiment was done[by whom?][when?] in Illinois, United States to allow going straight on red (like a right turn 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. 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.[7]
Image galleryedit
T Intersection Sign in Taiwan with no more road straight ahead
T Intersection Sign in Taiwan with side road on the left
T Intersection Sign in Taiwan with side road on the right
Y Intersection Sign in Taiwan
3-way Intersection Sign in Taiwan with side road on the right but not right angle
3-way Intersection Sign in Taiwan with side road on the left but not right angle
^Staff. "Technical Summary (FHWA-SA-10-002)". Access Management in the Vicinity of Intersections. Federal Highway Administration. Retrieved August 31, 2012.
^Joe G. Bared (January–February 2005). "Improving Signalized Intersections, Publication Number: FHWA-HRT-05-003". Public Roads. Federal Highway Administration. 68 (4). Retrieved August 31, 2012.
^An Applied Technology and Traffic Analysis Program (. Archived from the original on 2012-02-08. Retrieved 2007-10-12.)
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February 16, 2024
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For the type of railroad junction see Wye railroad A three way junction or three way intersection is a type of road intersection with three arms A Y junction or Y intersection generally has three arms of equal size coming at an acute or obtuse angle 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 Three way junction at Dragons Green geograph org uk 1578998 Contents 1 Right of way 2 Turns 3 Variations 4 Image gallery 5 ReferencesRight of way editSome three way junctions are controlled by traffic lights while others rely upon drivers to obey right of way 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 1 In other jurisdictions mainly in the U K USA 2 Australia and Taiwan 3 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 4 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 editWhen 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 5 6 Variations editAn experiment was done by whom when in Illinois United States to allow going straight on red like a right turn 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 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 7 Image gallery edit nbsp T Intersection Sign in Taiwan with no more road straight ahead nbsp T Intersection Sign in Taiwan with side road on the left nbsp T Intersection Sign in Taiwan with side road on the right nbsp Y Intersection Sign in Taiwan nbsp 3 way Intersection Sign in Taiwan with side road on the right but not right angle nbsp 3 way Intersection Sign in Taiwan with side road on the left but not right angleReferences edit SGI SGI Driver s Handbook Right of way Right of Way Clause 2 of Section 1 of Article 102 of the Road Traffic Security Rules s zh 道路交通安全規則 Li Jiasun 2022 09 14 Four Way Stops Rochester NY a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Staff Technical Summary FHWA SA 10 002 Access Management in the Vicinity of Intersections Federal Highway Administration Retrieved August 31 2012 Joe G Bared January February 2005 Improving Signalized Intersections Publication Number FHWA HRT 05 003 Public Roads Federal Highway Administration 68 4 Retrieved August 31 2012 An Applied Technology and Traffic Analysis Program ATTAP Archived from the original on 2012 02 08 Retrieved 2007 10 12 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