A junction is where two or more roads meet.
35-646: Ludgate Circus is a road junction in the City of London where Farringdon Street/New Bridge Street (the A201 ) crosses Fleet Street / Ludgate Hill . (Ludgate Hill is a gentle rise to St Paul's Cathedral .) Fleet Street was the only direct road between the cities of London and Westminster till the Embankment was opened in 1870. The Circus crosses the River Fleet , London's largest subterranean river . The concave-arced façades of
70-452: A grade-separated junction may be referred to as a grade separation or as an interchange – in contrast with an intersection , at-grade , a diamond crossing or a level crossing , which are not grade-separated. Roads with grade separation generally allow traffic to move freely, with fewer interruptions, and at higher overall speeds; this is why speed limits are typically higher for grade-separated roads. In addition, reducing
105-416: A highway) that they cross. However, grade-separated pedestrian crossings with steps introduce accessibility problems. Some crossings have lifts , but these can be time-consuming to use. Grade-separated roads that permit for higher speed limits can actually reduce safety due to 'weaving' (see below) as well as a perceived sense of safety. The term is most widely applied to describe a road junction in which
140-502: A location. In the United Kingdom and other countries, the practice of giving names to junctions emerged, to help travellers find their way. Junctions took the name of a prominent nearby business or a point of interest. As of the road networks increased in density and traffic flows followed suit, managing the flow of traffic across the junction became of increasing importance, to minimize delays and improve safety. The first innovation
175-414: A partial grade separation will accomplish more improvement than for a road), and because at-grade railway connections often take up significant space on their own. However, they require significant engineering effort, and are very expensive and time-consuming to construct. Grade-separated pedestrian and cycling routes often require modest space since they do not typically intersect with the facility (such as
210-410: A right turn (across oncoming traffic) in one turn). It also allows for diagonal crossings ( pedestrian scramble ) and reduces crossing distances for pedestrians. Intersections generally must manage pedestrian as well as vehicle traffic. Pedestrian aids include crosswalks , pedestrian-directed traffic signals ("walk light") and over/ underpasses . Walk lights may be accompanied by audio signals to aid
245-559: A right turn on red, and sometimes left on red depending on the geometry of the intersection in question, possible in many cases, often without stopping. Cyclists ideally have a protected bike lane on the approach to the intersection, separated by a concrete median with splay kerbs if possible, and have a protected bike lane width of at least 2 metres if possible (one way). In the Netherlands , most one way cycle paths are at least 2.5 metres wide. Bicycle traffic can be accommodated with
280-415: A setback crossing of the pedestrians and cyclists , generally between 1.5–7 metres of setback, a forward stop bar, which allows cyclists to stop for a traffic light well ahead of motor traffic who must stop behind the crosswalk. Separate signal staging or at least an advance green for cyclists and pedestrians is used to give cyclists and pedestrians no conflicts or a head start over traffic. The design makes
315-909: Is a four-way interchange on the German autobahn network. Autobahndreieck (literally "autobahn triangle"), short form dreieck , and abbreviated as AD, is a three-way interchange on the German autobahn network. At intersections , roads cross at-grade . They also can be further subdivided into those with and without signal controls. Signalized designs include advanced stop line , bowtie , box junction , continuous-flow intersection , continuous Green-T, double-wide, hook turn , jughandle , median u-turn, Michigan left , paired, quadrant , seagulls , slip lane , split, staggered , superstreet , Texas T , Texas U-turn and turnarounds . Non-signalized designs include unsignalized variations on continuous-flow 3 and 4-leg, median u-turn and superstreet, along with Maryland T/J, roundabout and traffic circle . In
350-419: Is fully grade-separated, i.e. traffic on one road does not have to stop at yield lines or signals on one road, but may have to do so when switching to the other: On roadways with grade-separated interchanges, weaving is a result of placing an exit ramp a short distance after an entry ramp, causing conflicts between traffic attempting to leave the roadway at the next junction and traffic attempting to enter from
385-708: Is known as a flying junction and one which is not a level junction . In 1897, the London and South Western Railway (LSWR) made use of a flying junction at Worting Junction south of Basingstoke to allow traffic on the Salisbury and Southampton routes to converge without conflicting movements; this became known as "Battledown Flyover". Also in Britain, the Southern Railway later made extensive use of flying junctions on other parts of its busy former LSWR main line. Today in Britain,
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#1732856197671420-632: Is whether or not the roads cross at the same or different elevations . More expensive, grade-separated interchanges generally offer higher throughput at higher cost. Single-grade intersections are lower cost and lower throughput. Each main type comes in many variants. At interchanges , roads pass above or below each other, using grade separation and slip roads . The terms motorway junction and highway interchange typically refer to this layout. They can be further subdivided into those with and without signal controls. Signalized ( traffic-light controlled) interchanges include such " diamond " designs as
455-514: The Great Central Railway , built between 1896 and 1899, was the first fully grade-separated railway of this type in the UK. This also applies to light rail and even to street cars . Attempts have been made to increase the capacity of railways by making tracks cross in a grade-separated manner, as opposed to the traditional use of flat crossings to change tracks. A grade-separated rail interchange
490-543: The River Thames before reaching Ludgate Circus. In 1990 however, St. Paul's Thameslink (later renamed City Thameslink) was opened on the proposed site, abolishing Ludgate Hill and Holborn Viaduct stations . In an episode of Rumpole of the Bailey is a wide shot of St Bride's Church and Ludgate Circus filmed c. 1988 , before City Thameslink station was built. The Post Office 's first coin-operated public call box
525-638: The diverging diamond , Michigan urban diamond, three-level diamond , and tight diamond. Others include center-turn overpass, contraflow left, single loop, and single-point urban overpass. Non-signalized designs include the cloverleaf , contraflow left, dogbone (restricted dumbbell), double crossover merging , dumbbell (grade-separated bowtie), echelon, free-flow interchange , partial cloverleaf , raindrop , single and double roundabouts (grade-separated roundabout ), single-point urban , stack , and windmill . Autobahnkreuz (literally "autobahn cross"), short form kreuz , and abbreviated as AK,
560-428: The traffic flow on other transit routes when they cross each other. The composition of such transport axes does not have to be uniform; it can consist of a mixture of roads , footpaths , railways , canals , or airport runways . Bridges (or overpasses , also called flyovers), tunnels (or underpasses ), or a combination of both can be built at a junction to achieve the needed grade separation. In North America,
595-570: The A4/M5 junction west of Bristol . Weaving can often cause side-on collisions on very fast roads with top speeds of up to 200 kilometres per hour, as well as the problem of blind spots. Where junctions have unusual designs weaving can be a problem other than on the main road. An example of this can be found at Junction 7 of the M6, where traffic joining the roundabout from the M6 Eastbound off-slip must weave with
630-640: The EU it is estimated that around 5,000 out of 26,100 people who are killed in car crashes are killed in a junction collision, in 2015, while it was around 8,000 in 2006. During the 2006–2015 decade, this means around 20% of road fatalities occur at junctions. By kind of users junctions fatalities are car users, 34%; pedestrians, 23%; motorcycle, 21%; pedal-cycle 12%; and other road users, the remaining. It has been considered that several causes might lead to fatalities; for instance: A number of features make this protected intersection much safer . A corner refuge island,
665-453: The Eastbound off-slip must leave. Weaving can be alleviated by using collector/distributor roads or braided ramps to separate entering and exiting traffic. In railway construction, grade separation also means the avoidance of level crossings by making any roads or footpaths crossing the line either pass under or over the railway on bridges . This greatly improves safety and is crucial to
700-505: The buildings facing the Circus were constructed between 1864 and 1875 using Haytor granite from Dartmoor in Devon transported via the prototype Haytor Granite Tramway . In Charles Dickens ' Dictionary of London (1879) the area was described as "Farringdon-circus". The name Ludgate , according to Stow in his 1598 Survey of London, was derived from the belief that the gate had been created by
735-515: The capacity of a road compared to an identical road with at-grade junctions. For instance, it is extremely uncommon to find an at-grade junction on a British motorway ; it is all but impossible on a U.S. Interstate Highway , though a few do exist. If traffic can traverse the junction from any direction without being forced to come to a halt, then the junction is described as fully grade separated or free-flowing . These junctions connect two freeways: These junctions connect two roads, but only one
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#1732856197671770-725: The complexity of traffic movements reduces the risk of accidents . Grade-separated road junctions are typically space-intensive, complicated, and costly, due to the need for large physical structures such as tunnels, ramps, and bridges. Their height can be obtrusive, and this, combined with the large traffic volumes that grade-separated roads attract, tend to make them unpopular to nearby landowners and residents. For these reasons, proposals for new grade-separated roads can receive significant public opposition. Rail-over-rail grade separations take up less space than road grade separations: because shoulders are not needed, there are generally fewer branches and side road connections to accommodate (because
805-571: The direct flow of traffic on one or more of the roads is not disrupted. Instead of a direct connection, traffic must use on and off ramps ( United States , Australia , New Zealand ) or slip roads ( United Kingdom , Ireland ) to access the other roads at the junction. The road which carries on through the junction can also be referred to as grade separated . Typically, large freeways , highways , motorways , or dual carriageways are chosen to be grade separated, through their entire length or for part of it. Grade separation drastically increases
840-613: The faster speed requires grade separation. Therefore, many high speed lines are elevated, especially in Taiwan and Japan , where population density alongside high speed lines is higher than in France, Italy or Germany. In the United States, a flying junction on the Nickel Plate Road through Cleveland , Ohio , United States was completed in 1913. The most frequent use was later found on
875-500: The former Pennsylvania Railroad main lines. The lines are included as part of the Northeast Corridor and Keystone Corridor now owned by Amtrak . The most complex of these junctions, near Philadelphia Zoo , handles railway traffic for Amtrak, SEPTA , New Jersey Transit , Norfolk Southern , CSX Transportation , and Conrail . In what is known as "area 1520" , which includes the former Soviet Union and other regions using
910-596: The low grade bike lanes in the roadway or higher grade and much safer protected bicycle paths that are physically separated from the roadway. In Manchester, UK, traffic engineers have designed a protected junction known as the Cycle-Optimised Signal (CYCLOPS) Junction. This design places a circulatory cycle track around the edge of the junction, with pedestrian crossing on the inside. This design allows for an all-red pedestrian / cyclist phase with reduced conflicts. Traffic signals are timed to allow cyclists to make
945-606: The pre-Roman British king of London, King Lud , as many of his contemporaries believed. When a new gate was erected a statue on it depicted him, along with one of Queen Elizabeth I . Had the Fleet line of the London Underground been built, it would have had a station at Ludgate Circus . However, the Fleet line's proposed route evolved into what is now the Jubilee line , which went south of
980-536: The previous junction. This situation is most prevalent either where the junction designer has placed the on-slip to the road before the off-slip at a junction (for example, the cloverleaf interchange ), or in urban areas with many close-spaced junctions. The ring road of Coventry , England , is a notorious example, as are parts of the southern M25, the London orbital motorway , the M6/M5 junction north-west of Birmingham , and
1015-540: The safe operation of high-speed lines. The construction of new level crossings is generally not permitted, especially for high speed railway lines and level crossings are increasingly less common due to the increase of both road and rail traffic. Efforts to remove level crossings are done in the UK by Network Rail and in Melbourne as part of the Level Crossing Removal Project . The London Extension of
1050-664: The same gauge, the most complicated grade-separation railpoint is found at Liubotyn in Ukraine . Footbridges and subways (called underpasses in North America as well as in the United Kingdom when referring to roads) may be employed to allow pedestrians and cyclists to cross busy or fast streets. They are often used over and under motorways since at grade pedestrian crossings are generally not permitted. Same can be said for railways. Though introduced to Central Park in New York City in
1085-400: The tightly grouped nest of flying junctions to the north of Clapham Junction railway station —although technically a combination of many junctions—handle more than 4,000 trains per day (about one train every 15 seconds). Virtually all major railway lines no longer cross (forming an 'X' shape ) at flat level (although many diverge - i.e. 'Y' shape). On almost all high-speed railway lines,
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1120-537: The traffic already on the roundabout wishing to use the M6 Westbound on-slip. This is as a result of the slip roads on the west side of the junction connecting to the roundabout on the inside of the eastern arc rather than the outside of the western arc as is normal. The two slip-roads are connected by a single lane on the inside of the roundabout, which traffic wishing to use the Westbound on-slip must join, and traffic from
1155-449: 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. Grade separation In civil engineering (more specifically highway engineering ), grade separation is a method of aligning a junction of two or more surface transport axes at different heights (grades) so that they will not disrupt
1190-469: Was installed in 1906 at its Ludgate Circus branch, by the British subsidiary of Western Electric (incorporated in Britain in 1910). Junction (road) Roads began as a means of linking locations of interest: towns , forts and geographic features such as river fords . Where roads met outside of an existing settlement, these junctions often led to a new settlement. Scotch Corner is an example of such
1225-521: Was to add traffic control devices, such as stop signs and traffic lights that regulated traffic flow. Next came lane controls that limited what each lane of traffic was allowed to do while crossing. Turns across oncoming traffic might be prohibited, or allowed only when oncoming and crossing traffic was stopped. This was followed by specialized junction designs that incorporated information about traffic volumes, speeds, driver intent and many other factors. The most basic distinction among junction types
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