In the field of road transport, an intersection is a road junction where two or more roads either meet or cross at grade (they are at the same level). Road transport ( British English) or road transportation ( American English) is Transport on Roads of passengers or goods A junction, when discussed in the context of Transport, is a location where Traffic can change between different routes directions or sometimes modes of travel A road is an identifiable route, way or path between two or more places. An at-grade intersection is a junction at which two or more transport axes cross at the same Level (or grade) LEVEL is a Computer and video games Magazine originating in the Czech Republic with branches in Romania and Turkey Such a road junction may also be called a crossroads. A crossroads (the word rarely appears in singular is a Road junction, where two or more Roads meet (there are three or more arms
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Types of intersections
Same may classify intersections as 3-way, 4-way, 5-way, 6-way, etc. depending on the number of road segments (arms) that come together at the intersection.
- 3-way intersection - A junction between three road segments (arms) is a T junction (two arms form one road) or a Y-junction. A 3-way junction (or 3-way intersection) is a type of Road junction with three arms
- 4-way intersections are the most common, because they usually involve a crossing over of two streets or roads. In areas where there blocks and in some other cases, the crossing streets or roads are perpendicular to each other. A city block, urban block or simply block is a central element of Urban planning and Urban design. In Geometry, two lines or planes (or a line and a plane are considered perpendicular (or orthogonal) to each other if they form congruent 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.
- 5-way intersections are less common but still exist, especially in urban areas with non-rectangular blocks.
- 6-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.
- Seven or more such segments coming together at a single intersection are rare.
Another way of classifying intersections is by traffic control:
- Uncontrolled intersections, without signs or signals (or sometimes with a warning sign). An uncontrolled intersection is a road intersection where no traffic lights or signs are used to indicate the right-of-way Priority 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. Traffic on Roads may consist of Pedestrians ridden or herded Animals Vehicles Streetcars and other Conveyances either singly 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. A stop sign is a Traffic sign, usually erected at Road junctions that instructs drivers to stop and then to proceed only if the way ahead is clear 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. The traffic light, also known as traffic signal, stop light, traffic lamp, stop-and-go lights, robot or semaphore,
- A traffic circle is a type of intersection at which traffic streams are directed around a circle. A traffic circle is an intersection with a circular shape and usually a central island Types of traffic circles include roundabouts, 'mini-roundabouts', 'rotaries', "STOP"-controlled circles, and signal-controlled circles. A roundabout is a type of Road junction at which Traffic enters a one-way stream around a central island 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. A box junction is a Traffic control measure designed to prevent Gridlock at busy Road junctions The surface of the junction is marked with a criss-cross
- Some intersections employ indirect left turns to increase capacity and reduce delays. The Michigan left combines a right turn and a U-turn. A Michigan left, sometimes known as a median U-turn, median U-turn crossover, or Boulevard Turnaround, is an Automobile Traffic maneuver Jughandle lefts diverge to the right, then curve to the left, converting a left turn to a crossing maneuver. A jughandle is a type of ramp or Slip road that changes the way traffic turns left (when driving on the right) These techniques are generally used in conjunction with signal-controlled intersections, although they may also be used at stop-controlled intersections.
Turns
At same-grade intersections, turns are usually allowed, but often regulated to avoid interference or collision with other traffic. If the crossing street is a one-way street, a turn into the opposing direction is not allowed, as indicated by "ONE WAY" or "NO LEFT TURN" or "NO RIGHT TURN" signs. In a few other cases, certain turns may be not allowed or limited by regulatory signs or signals, such as a sign saying "NO TURN ON RED" (no turn allowed when a red light is on). In the absence of lane markings indicating otherwise, left turns should be made from the leftmost lane and right turns from the rightmost lane to avoid collision or blocking of traffic going straight.
Turn lanes
At some intersections where vehicles travel on the right side of the road, there are left turn lanes where the street/road approaches the intersection. For example in the intersection shown in the following diagram, there are left turn lanes in the east-west street for traffic approaching the intersection in the eastbound and westbound directions.
These left turn lanes are marked with an arrow bending into the direction of the left turn which is to be made from that lane only. The word "ONLY" in those lanes means that vehicles may only use them to make a left turn from there. In some other cases, a double-headed arrow may indicate vehicles may travel in either one of two directions from that lane. Traffic signals facing vehicles in left turn lanes often have a special green left turn arrow, indicating vehicles may turn left unhindered by oncoming traffic when this green arrow light is on. Even though the north-south street does not have left turn lanes, traffic may still turn left (unless otherwise not allowed) from the leftmost lane facing the intersection northbound or southbound. When there is no green left turn arrow, vehicles from that direction may enter the intersection to turn left only when there is a green light facing them and must yield to all oncoming traffic. There are intersections with no left turn lanes and many major intersections with left turn lanes for traffic from all directions. Streets without left turn lanes usually either have less traffic than streets with left turn lanes or are older streets where it is difficult to widen the street to accommodate the extra lane. Depending on the intersection, many other combinations of traffic signals (such as green, yellow, or red left or right arrows) and left or right turn lanes are possible. In areas where vehicles travel on the left side of the road, the preceding discussion about left turns applies to right turns instead. Often parallel parking on the side of a street is not allowed close to an intersection to allow traffic to flow through better near the intersection. Parallel parking is a method of Parking a Vehicle in line with other parked cars
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 will be slightly lower in urban areas. [1]
Other markings
In some places, wider white stop lines (see preceding diagram) indicate where vehicles should stop at an intersection when there is a stop sign or a red light in a traffic signal facing them. Some intersections have pedestrian crosswalks designated on the street pavement. Crosswalk button neJPG|right|thumb|The button one pushes to activate the crosswalk signal Some possible markings for crosswalks are shown as examples. Note that the stop line is positioned to not allow stopped vehicles to block the crosswalk.
References
- ^ D. W. Harwood,et al. , Safety Effectiveness of Intersection Left- and Right-Turn Lanes, Federal Highway Administration Office of Safety Research and Development , 2002, http://www.tfhrc.gov/safety/pubs/02089/02089techbrief.htm
See also
External links
An at-grade intersection is a junction at which two or more transport axes cross at the same Level (or grade) In the field of Road transport, an interchange is a road junction that typically A junction, when discussed in the context of Transport, is a location where Traffic can change between different routes directions or sometimes modes of travelDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic