Three-way junction

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Three way junction at Dragons Green - geograph.org.uk - 1578998 Three way junction at Dragons Green - geograph.org.uk - 1578998.jpg
Three way junction at Dragons Green - geograph.org.uk - 1578998

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.

Contents

Right-of-way

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., 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] while in other jurisdictions, chiefly in the U.K. and Australia, 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), for every vehicle turning left or (if two vehicles both turn right) for the vehicle approaching from the left (and a road going straight ahead at a three-way junction is normally marked as a priority road). Taiwan (the Republic of China), which has right-hand traffic, has a similar T-junction rule, which, however, is vice verse, obliging a driver turning left to yield for vehicles turning right or (when two drivers both turn left) for the vehicle approaching from the right. [2]

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. [3] [4]

Variations

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. [5]

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References

  1. SGI. "SGI - Driver's Handbook - Right of way".
  2. Clause 2 of Section 1 of Article 102 of the Road Traffic Security Rules (s:zh:道路交通安全規則)
  3. Staff. "Technical Summary (FHWA-SA-10-002)". Access Management in the Vicinity of Intersections. Federal Highway Administration . Retrieved August 31, 2012.
  4. 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.
  5. An Applied Technology and Traffic Analysis Program ( "ATTAP". Archived from the original on 2012-02-08. Retrieved 2007-10-12.)