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Intersection (road)

January 14, 2023

This article primarily reflects practice in jurisdictions where vehicles are driven on the right. If not otherwise specified, "right" and "left" can be reversed to reflect jurisdictions where vehicles are driven on the left.

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.

The intersection between Ayala Avenue and Makati Avenue in Makati, Philippines
An intersection in rural Grande Champagne, France

Types

Road segments

One way to classify intersections is by the number of road segments (arms) that are involved.

  • A three-way intersection is a junction between three road segments (arms): a T junction when two arms form one road, or a Y junction, the latter also known as a fork if approached from the stem of the Y.
  • A four-way intersection, or crossroads, usually involves a crossing over of two streets or roads. In areas where there are blocks and in some other cases, the crossing streets or roads are perpendicular to each other. However, two roads may cross at a different angle. In a few cases, the junction of two road segments may be offset from each when reaching an intersection, even though both ends may be considered the same street.
  • Six-way intersections usually involve a crossing of three streets at one junction; for example, a crossing of two perpendicular streets and a diagonal street is a rather common type of 6-way intersection.
  • Five, seven or more approaches to a single intersection, such as at Seven Dials, London, are not common.
 
Intersection along the Veterans Memorial Parkway, an at-grade limited-access road in London, Ontario.

Traffic controls

 
Intersection with traffic signs and traffic lights in Klaukkala, Finland

Another way of classifying intersections is by traffic control technology:

  • Uncontrolled intersections, without signs or signals (or sometimes with a warning sign). Priority (right-of-way) rules may vary by country: on a 4-way intersection traffic from the right often has priority; on a 3-way intersection either traffic from the right has priority again, or traffic on the continuing road. For traffic coming from the same or opposite direction, that which goes straight has priority over that which turns off.
  • Yield-controlled intersections may or may not have specific "YIELD" signs (known as "GIVE WAY" signs in some countries).
  • Stop-controlled intersections have one or more "STOP" signs. Two-way stops are common, while some countries also employ four-way stops.
  • Signal-controlled intersections depend on traffic signals, usually electric, which indicate which traffic is allowed to proceed at any particular time.

Lane design

Turns

At intersections, turns are usually allowed, but are often regulated to avoid interference with other traffic. Certain turns may be not allowed or may be limited by regulatory signs or signals, particularly those that cross oncoming traffic. Alternative designs often attempt to reduce or eliminate such potential conflicts.

Turn lanes

At intersections with large proportions of turning traffic, turn lanes (also known as turn bays)[2] may be provided. For example, in the intersection shown in the diagram,[clarification needed] left turn lanes are present in the right-left street.

Turn lanes allow vehicles, to cross oncoming traffic (i.e., a left turn in right-side driving countries, or a right turn in left-side driving countries), or to exit a road without crossing traffic (i.e., a right turn in right-side driving countries, or a left turn in left-side driving countries). Absence of a turn lane does not normally indicate a prohibition of turns in that direction. Instead, traffic control signs are used to prohibit specific turns.[3]

Turn lanes can increase the capacity of an intersection or improve safety. Turn lanes can have a dramatic effect on the safety of a junction. In rural areas, crash frequency can be reduced by up to 48% if left turn lanes are provided on both main-road approaches at stop-controlled intersections. At signalized intersections, crashes can be reduced by 33%. Results are slightly lower in urban areas.[4]

Turn lanes are marked with an arrow bending into the direction of the turn which is to be made from that lane. Multi-headed arrows indicate that vehicle drivers may travel in any one of the directions pointed to by an arrow.

Turn signals

 
"Right turn on red" traffic light in Belgrade, Serbia, right turn only after pedestrians and traffic pass from left.

Traffic signals facing vehicles in turn lanes often have arrow-shaped indications. North America uses various indication patterns. Green arrows indicate protected turn phases, when vehicles may turn unhindered by oncoming traffic. Red arrows may be displayed to prohibit turns in that direction. Red arrows may be displayed along with a circular green indication to show that turns in the direction of the arrow are prohibited, but other movements are allowed. In some jurisdictions, a red arrow prohibits a turn on red.[5] In Europe, if different lanes have differing phases, red, yellow and green traffic lights corresponding to each lane have blacked-out areas in the middle in the shape of arrows indicating the direction(s) drivers in that lane may travel in. This makes it easier for drivers to be aware which traffic light they need to pay attention to. A green arrow may also be provided; when it is on, drivers heading in the direction of the arrow may proceed, but must yield to all other vehicles. This is similar to the right turn on red in the US.[6]

Disadvantages to turn lanes include increased pavement area, with associated increases in construction and maintenance costs, as well as increased amounts of stormwater runoff. They also increase the distance over which pedestrians crossing the street are exposed to vehicle traffic. If a turn lane has a separate signal phase, it often increases the delay experienced by oncoming through traffic. Without a separate phase, left crossing traffic does not get the full safety benefit of the turn lane.

Lane management

Alternative intersection configurations, formerly called unconventional intersections, can manage turning traffic to increase safety and intersection throughput.[7] These include the Michigan left/Superstreet (RCUT/MUT) and continuous flow intersection (CFI/DLT), to improve traffic flow, and also interchange types like Diverging diamond interchange (DDI/DCD) design as part of the Federal Highway Administration's Every Day Counts initiative which started in 2012.[8]

 
Diagram of an example intersection of two-way streets as seen from above (traffic flows on the right side of the road). The east-west street has left turn lanes from both directions, but the north-south street does not have left turn lanes at this intersection. The east-west street traffic lights also have green left turn arrows to show when unhindered left turns can be made. Some possible markings for crosswalks are shown as examples.

Vulnerable road users

Vulnerable road users include pedestrians, cyclists, motorcyclists, and individuals using motorized scooters and similar devices. Compared to people who are in motor vehicles (like cars and trucks), they are much more likely to suffer catastrophic or fatal injuries at an intersection.

Pedestrians

 
Times Square is the hub of the Broadway theater district and a major cultural venue in Midtown Manhattan, New York City. The pedestrian intersection also has one of the highest annual attendance rates of any tourist attraction in the world, estimated at 60 million.[9]

Intersections generally must manage pedestrian as well as vehicle traffic. Pedestrian aids include crosswalks, pedestrian-directed traffic signals ("walk light") and over/underpasses. Traffic signals can be time consuming to navigate, especially if programmed to prioritise vehicle flow over pedestrians, while over and underpasses which rely on stairs are inaccessible to those who can't climb them. Walk lights may be accompanied by audio signals to aid the visually impaired. Medians can offer pedestrian islands, allowing pedestrians to divide their crossings into a separate segment for each traffic direction, possibly with a separate signal for each.

 
Famous intersection of Highways 61 and 49 in Clarksdale, Mississippi sung about by Robert Johnson

Some intersections display red lights in all directions for a period of time. Known as a pedestrian scramble, this type of vehicle all-way stop allows pedestrians to cross safely in any direction, including diagonally. All green for non motorists is known from the crossing at Shibuya Station, Tokyo.[10]

In 2020, NHTSA reported that more than 50% of pedestrian deaths in the United States (3,262 total) were attributed to failure to yield the right of way-- which typically occurs at intersections. [11]

Cyclists and motorcyclists

Poor visibility at junctions can lead to drivers colliding with cyclists and motorcyclists. Some junctions use advanced stop lines which allow cyclists to filter to the front of a traffic queue which makes them more visible to drivers.

Safety

A European study found that in Germany and Denmark, the most important crash scenario involving vulnerable road users was:

  • motor vehicle turning right/left while cyclist going straight;
  • motor vehicle turning right/left while pedestrian crossing the intersection approach.[12]


These findings are supported by data elsewhere. According to the U.S. National Highway Traffic Safety Administration, roughly half of all U.S. car crashes occurred at intersections or were intersection related in 2019.[13]

At grade railways

Main article: Level crossings

In the case of railways or rail tracks the term at grade applies to a rail line that is not on an embankment nor in an open cut. As such, it crosses streets and roads without going under or over them. This requires level crossings. At-grade railways may run along the median of a highway. The opposite is grade-separated. There may be overpasses or underpasses.

See also

References

  1. ^ Steyn, Hermanus. (2014). Displaced Left-turn Intersection Informational Guide. Washington, D.C.: U.S. Department of Transportation, Federal Highway Administration.
  2. ^ "Manual on Uniform Traffic Control Devices (MUTCD), Part 1" (PDF). U.S. DOT, Federal Highway Administration. December 11, 2009. Retrieved November 28, 2011.
  3. ^ "Traffic Signals Brochure - How is it Determined if a Traffic Signal is Needed?". Maryland State Highway Administration.
  4. ^ D.W. Harwood, et al., Safety Effectiveness of Intersection Left- and Right-Turn Lanes, Federal Highway Administration Office of Safety Research and Development, 2002, [1]
  5. ^ New York State Driver's Manual, Chapter 4.
  6. ^ Vienna Convention on Road Signs and Signals
  7. ^ Badger, Emily. "Could These Crazy Intersections Make Us Safer?". The Atlantic Cities. Atlantic Media Company. Retrieved 29 January 2013.
  8. ^ https://rosap.ntl.bts.gov/view/dot/29474/dot_29474_DS1.pdf?download-document-submit=Download[bare URL PDF]
  9. ^ Rachel Sugar (December 19, 2016). "More tourists visited NYC in 2016 than ever before". Vox Media. Retrieved April 24, 2018.
  10. ^ "Saturday afternoon at Shibuya Crossing, Tokyo". YouTube. April 21, 2007. Archived from the original on 2021-11-14.
  11. ^ "Table 100; Pedestrians Killed, by Related Factors, 2020". NHTSA. 2021. Retrieved December 15, 2022.{{cite web}}: CS1 maint: url-status (link)
  12. ^ "Indev Project -" (PDF).
  13. ^ "Traffic Safety Facts 2019". National Highway Traffic Safety Administration. 2020.

External links

  • Traffic flow measured on 30 different 4-way junctions, by euverus, December 4, 2017 in the video game Cities: Skylines
 
Wikimedia Commons has media related to Road junctions.

January 14, 2023
intersection, road, this, article, primarily, reflects, practice, jurisdictions, where, vehicles, driven, right, otherwise, specified, right, left, reversed, reflect, jurisdictions, where, vehicles, driven, left, this, article, multiple, issues, please, help, . This article primarily reflects practice in jurisdictions where vehicles are driven on the right If not otherwise specified right and left can be reversed to reflect jurisdictions where vehicles are driven on the left This article has multiple issues Please help improve it or discuss these issues on the talk page Learn how and when to remove these template messages The examples and perspective in this article may not represent a worldwide view of the subject You may improve this article discuss the issue on the talk page or create a new article as appropriate November 2011 Learn how and when to remove this template message This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Intersection road news newspapers books scholar JSTOR January 2008 Learn how and when to remove this template message Learn how and when to remove this template message 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 Intersection at Tverskaya Zastava Square in Moscow Russia The intersection between Ayala Avenue and Makati Avenue in Makati Philippines An intersection in rural Grande Champagne France Contents 1 Types 1 1 Road segments 1 2 Traffic controls 1 3 Lane design 2 Turns 2 1 Turn lanes 2 2 Turn signals 2 3 Lane management 3 Vulnerable road users 3 1 Pedestrians 3 2 Cyclists and motorcyclists 4 Safety 5 At grade railways 6 See also 7 References 8 External linksTypes EditRoad segments Edit One way to classify intersections is by the number of road segments arms that are involved A three way intersection is a junction between three road segments arms a T junction when two arms form one road or a Y junction the latter also known as a fork if approached from the stem of the Y A four way intersection or crossroads usually involves a crossing over of two streets or roads In areas where there are blocks and in some other cases the crossing streets or roads are perpendicular to each other However two roads may cross at a different angle In a few cases the junction of two road segments may be offset from each when reaching an intersection even though both ends may be considered the same street Six way intersections usually involve a crossing of three streets at one junction for example a crossing of two perpendicular streets and a diagonal street is a rather common type of 6 way intersection Five seven or more approaches to a single intersection such as at Seven Dials London are not common Intersection along the Veterans Memorial Parkway an at grade limited access road in London Ontario Traffic controls Edit Intersection with traffic signs and traffic lights in Klaukkala Finland Another way of classifying intersections is by traffic control technology Uncontrolled intersections without signs or signals or sometimes with a warning sign Priority right of way rules may vary by country on a 4 way intersection traffic from the right often has priority on a 3 way intersection either traffic from the right has priority again or traffic on the continuing road For traffic coming from the same or opposite direction that which goes straight has priority over that which turns off Yield controlled intersections may or may not have specific YIELD signs known as GIVE WAY signs in some countries Stop controlled intersections have one or more STOP signs Two way stops are common while some countries also employ four way stops Signal controlled intersections depend on traffic signals usually electric which indicate which traffic is allowed to proceed at any particular time Lane design Edit A traffic circle is a type of intersection at which traffic streams are directed around a circle Types of traffic circles include roundabouts mini roundabouts rotaries STOP controlled circles and signal controlled circles Some people consider roundabouts to be a distinct type of intersection from traffic circles with the distinction based on certain differences in size and engineering A box junction can be added to an intersection generally prohibiting entry to the intersection unless the exit is clear Some unconventional or alternative intersections employ indirect left turns to increase capacity and reduce delays The Michigan left combines a right turn and a U turn Jughandle lefts diverge to the right then curve to the left converting a left turn to a crossing maneuver similar to throughabouts These techniques are generally used in conjunction with signal controlled intersections although they may also be used at stop controlled intersections 1 Other designs include advanced stop lines parallel flow and continuous flow intersections hook turns quadrants seagull intersections slip lanes staggered junctions in American English referred to as doglegs superstreets Texas Ts Texas U turns and turnarounds clarification needed A roundabout and its variants like turbo roundabouts bowties and distributing circles like traffic circles and right in right out RIRO intersections clarification needed Turns EditAt intersections turns are usually allowed but are often regulated to avoid interference with other traffic Certain turns may be not allowed or may be limited by regulatory signs or signals particularly those that cross oncoming traffic Alternative designs often attempt to reduce or eliminate such potential conflicts Turn lanes Edit At intersections with large proportions of turning traffic turn lanes also known as turn bays 2 may be provided For example in the intersection shown in the diagram clarification needed left turn lanes are present in the right left street Turn lanes allow vehicles to cross oncoming traffic i e a left turn in right side driving countries or a right turn in left side driving countries or to exit a road without crossing traffic i e a right turn in right side driving countries or a left turn in left side driving countries Absence of a turn lane does not normally indicate a prohibition of turns in that direction Instead traffic control signs are used to prohibit specific turns 3 Turn lanes can increase the capacity of an intersection or improve safety Turn lanes can have a dramatic effect on the safety of a junction In rural areas crash frequency can be reduced by up to 48 if left turn lanes are provided on both main road approaches at stop controlled intersections At signalized intersections crashes can be reduced by 33 Results are slightly lower in urban areas 4 Turn lanes are marked with an arrow bending into the direction of the turn which is to be made from that lane Multi headed arrows indicate that vehicle drivers may travel in any one of the directions pointed to by an arrow Turn signals Edit Right turn on red traffic light in Belgrade Serbia right turn only after pedestrians and traffic pass from left Traffic signals facing vehicles in turn lanes often have arrow shaped indications North America uses various indication patterns Green arrows indicate protected turn phases when vehicles may turn unhindered by oncoming traffic Red arrows may be displayed to prohibit turns in that direction Red arrows may be displayed along with a circular green indication to show that turns in the direction of the arrow are prohibited but other movements are allowed In some jurisdictions a red arrow prohibits a turn on red 5 In Europe if different lanes have differing phases red yellow and green traffic lights corresponding to each lane have blacked out areas in the middle in the shape of arrows indicating the direction s drivers in that lane may travel in This makes it easier for drivers to be aware which traffic light they need to pay attention to A green arrow may also be provided when it is on drivers heading in the direction of the arrow may proceed but must yield to all other vehicles This is similar to the right turn on red in the US 6 Disadvantages to turn lanes include increased pavement area with associated increases in construction and maintenance costs as well as increased amounts of stormwater runoff They also increase the distance over which pedestrians crossing the street are exposed to vehicle traffic If a turn lane has a separate signal phase it often increases the delay experienced by oncoming through traffic Without a separate phase left crossing traffic does not get the full safety benefit of the turn lane Lane management Edit Alternative intersection configurations formerly called unconventional intersections can manage turning traffic to increase safety and intersection throughput 7 These include the Michigan left Superstreet RCUT MUT and continuous flow intersection CFI DLT to improve traffic flow and also interchange types like Diverging diamond interchange DDI DCD design as part of the Federal Highway Administration s Every Day Counts initiative which started in 2012 8 Diagram of an example intersection of two way streets as seen from above traffic flows on the right side of the road The east west street has left turn lanes from both directions but the north south street does not have left turn lanes at this intersection The east west street traffic lights also have green left turn arrows to show when unhindered left turns can be made Some possible markings for crosswalks are shown as examples Vulnerable road users EditVulnerable road users include pedestrians cyclists motorcyclists and individuals using motorized scooters and similar devices Compared to people who are in motor vehicles like cars and trucks they are much more likely to suffer catastrophic or fatal injuries at an intersection Pedestrians Edit Times Square is the hub of the Broadway theater district and a major cultural venue in Midtown Manhattan New York City The pedestrian intersection also has one of the highest annual attendance rates of any tourist attraction in the world estimated at 60 million 9 Intersections generally must manage pedestrian as well as vehicle traffic Pedestrian aids include crosswalks pedestrian directed traffic signals walk light and over underpasses Traffic signals can be time consuming to navigate especially if programmed to prioritise vehicle flow over pedestrians while over and underpasses which rely on stairs are inaccessible to those who can t climb them Walk lights may be accompanied by audio signals to aid the visually impaired Medians can offer pedestrian islands allowing pedestrians to divide their crossings into a separate segment for each traffic direction possibly with a separate signal for each Famous intersection of Highways 61 and 49 in Clarksdale Mississippi sung about by Robert Johnson Some intersections display red lights in all directions for a period of time Known as a pedestrian scramble this type of vehicle all way stop allows pedestrians to cross safely in any direction including diagonally All green for non motorists is known from the crossing at Shibuya Station Tokyo 10 In 2020 NHTSA reported that more than 50 of pedestrian deaths in the United States 3 262 total were attributed to failure to yield the right of way which typically occurs at intersections 11 Cyclists and motorcyclists Edit Poor visibility at junctions can lead to drivers colliding with cyclists and motorcyclists Some junctions use advanced stop lines which allow cyclists to filter to the front of a traffic queue which makes them more visible to drivers Safety EditA European study found that in Germany and Denmark the most important crash scenario involving vulnerable road users was motor vehicle turning right left while cyclist going straight motor vehicle turning right left while pedestrian crossing the intersection approach 12 These findings are supported by data elsewhere According to the U S National Highway Traffic Safety Administration roughly half of all U S car crashes occurred at intersections or were intersection related in 2019 13 At grade railways EditMain article Level crossings In the case of railways or rail tracks the term at grade applies to a rail line that is not on an embankment nor in an open cut As such it crosses streets and roads without going under or over them This requires level crossings At grade railways may run along the median of a highway The opposite is grade separated There may be overpasses or underpasses See also EditGore road Triangular plot of land used in traffic infrastructure Grade separation Type of road junction Interchange road Road junction that uses grade separation Junction road Junction traffic Roundabout Street StreetcornerReferences Edit Steyn Hermanus 2014 Displaced Left turn Intersection Informational Guide Washington D C U S Department of Transportation Federal Highway Administration Manual on Uniform Traffic Control Devices MUTCD Part 1 PDF U S DOT Federal Highway Administration December 11 2009 Retrieved November 28 2011 Traffic Signals Brochure How is it Determined if a Traffic Signal is Needed Maryland State Highway Administration D W Harwood et al Safety Effectiveness of Intersection Left and Right Turn Lanes Federal Highway Administration Office of Safety Research and Development 2002 1 New York State Driver s Manual Chapter 4 Vienna Convention on Road Signs and Signals Badger Emily Could These Crazy Intersections Make Us Safer The Atlantic Cities Atlantic Media Company Retrieved 29 January 2013 https rosap ntl bts gov view dot 29474 dot 29474 DS1 pdf download document submit Download bare URL PDF Rachel Sugar December 19 2016 More tourists visited NYC in 2016 than ever before Vox Media Retrieved April 24 2018 Saturday afternoon at Shibuya Crossing Tokyo YouTube April 21 2007 Archived from the original on 2021 11 14 Table 100 Pedestrians Killed by Related Factors 2020 NHTSA 2021 Retrieved December 15 2022 a href Template Cite web html title Template Cite web cite web a CS1 maint url status link Indev Project PDF Traffic Safety Facts 2019 National Highway Traffic Safety Administration 2020 External links EditTraffic flow measured on 30 different 4 way junctions by euverus December 4 2017 in the video game Cities Skylines Wikimedia Commons has media related to Road junctions Retrieved from https en wikipedia org w index php title Intersection road amp oldid 1127576204, wikipedia, wiki, book, books, library,

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