In the field of road transport, an interchange is a road junction that typically utilizes grade separation, and one or more ramps, to permit traffic on at least one road to pass through the junction without crossing any other traffic stream. 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 Grade separation is the process of aligning a junction of two or more transport axes at different heights ( A road is an identifiable route, way or path between two or more places. It differs from an intersection, at which roads cross at grade. 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 An at-grade intersection is a junction at which two or more transport axes cross at the same Level (or grade) Interchanges are almost always used when at least one of the roads is a freeway, though they may occasionally be used at junctions between two surface streets.
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Terminology
Note: The descriptions of road junctions are for countries where vehicles drive on the right side of the road. Vehicles, derived from the Latin word vehiculum, are non-living Means of transport. Right-hand traffic and left-hand traffic mean regulations requiring all traffic to keep either to the left or the right side of the Road. For countries where driving is on the left the layout of the junctions is the same, only left/right is reversed.
- A freeway junction or highway interchange (in the U.S.) or motorway junction (in the UK) is a type of road junction, linking one motorway to another; to other roads; or sometimes to just a motorway service station. The United States of America —commonly referred to as the The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Motorway is a term for both a type of Road and a classification or designation Motorway is a term for both a type of Road and a classification or designation In the UK, all junctions on a motorway with other roads are numbered—the first being called "Junction 1", etc. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located In the U. S. , interchanges are either numbered according to cardinal interchange number, or by mileage.
- A highway ramp (as in exit ramp and entrance ramp) or slip road is a short section of road which allows vehicles to enter or exit a freeway (motorway). Motorway is a term for both a type of Road and a classification or designation
- A directional ramp always tends toward the desired direction of travel. This means that a ramp that makes a left turn exits from the left side of the roadway (a left exit). Left directional ramps are relatively uncommon as the left lane is usually reserved for high-speed through traffic. Right ramps are almost always directional.
- A non-directional ramp goes in a direction opposite to the desired direction of travel. Many loop ramps (as in a cloverleaf) are non-directional.
- A semi-directional ramp exits a road in a direction opposite from the desired direction of travel, but then turns toward the desired direction of travel. Many 'flyover ramps' (as in a stack) are semi-directional. An overpass (called a flyover in the UK and most Commonwealth countries is a Bridge, Road, Railway or
- A U-turn ramp leaves the road in one driving direction, turns over or under it and rejoins in the opposite direction.
Weaving is an undesirable situation in which traffic veering right and traffic veering left must cross paths within a limited distance, to merge with traffic on the through lane. In the worst circumstances, a large portion of through traffic must change lanes to stay on the same roadway. Weaving creates both safety and capacity problems. Some interchanges use collector/distributor roads to deal with weaving—while doing so does not eliminate the problem entirely, it separates the weaving traffic from the freeway's main lanes, thus improving traffic flow. A collector/distributor road, often abbreviated as C/D road, is a one-way road next to a Freeway that is used for some or all of the ramps that would otherwise merge Some areas that had such bad junctions have gone through the expensive process of "unweaving the weave" to improve traffic flow. Another way to avoid weaving is to have braided ramps, in which an onramp passes over or under an offramp using an overpass structure, which is commonly used on Highway 407 and other 400-series highways. Highway 407, officially called the 407 Express Toll Route (ETR, is a Tollway located in the Greater Toronto Area, southern Ontario, Canada The 400-series highways are a network of controlled-access Freeways throughout the southern portion of the province of Ontario, Canada, forming a special
The German Autobahn system splits Autobahn-to-Autobahn interchanges into two types—Autobahnkreuz (AK, translates as "motorway cross"), a crossing of two Autobahns (or something more complicated), and Autobahndreieck (AD, translates as "motorway triangle"), an interchange where one of the Autobahns ends. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. (German ˈaʊtoːbaːn plural Autobahnen; English /ˈɔːtəʊbɑːn/ is the German word for a major high- Speed Road restricted to motor
Complete interchanges
A complete interchange has enough ramps to provide access from any direction of any road in the junction to any direction of any other road in the junction.
Barring u-turns, a complete interchange between two freeways requires eight ramps, while a complete interchange between a freeway and another road (not a freeway) requires at least four ramps. Using u-turns these numbers can be halved to four and two respectively, by making cars that want to turn left pass by the other road first, then make a u-turn and turn right. The use of u-turn ramps is common in less wealthy countries.
The general rule today is that freeways should have at least one mile between interchanges to prevent excessive weaving between entering and leaving traffic. Unfortunately, most older freeway interchanges do not follow this rule (and are congested as a result).
Between two freeways
Four-way
- A cloverleaf is a two-level four-way interchange in which left turns are handled by loop ramps. Arnhem ( ( South Guelderish: Èrnem) is a city and Municipality, situated in the eastern part of the Netherlands. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Overview Cloverleaf interchanges viewed from overhead or on maps resemble the leaves of a Four-leaf clover. To go left, vehicles first pass either over or under the other road, then bear right onto a one-way ramp that loops 270 degrees to the right and then merges onto the intersecting road. (In countries where cars drive on the left, this is a left turn. ) The major advantage of cloverleafs is that they require only one bridge, which makes such junctions cheap if land is plentiful. A major problem with cloverleafs is weaving (see definition of weaving, above). Cloverleafs also have a considerable land consumption which means that while they are common in the United States, Canada (mainly parclos), Germany, and Netherlands, only four such junctions are found in the land-scarce United Kingdom, with just one on the motorway network (partial cloverleaf exists where the M25 meets the M40 west of London). The United States of America —commonly referred to as the Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page The parclo interchange (a Portmanteau of partial cloverleaf interchange) is a modification of a Cloverleaf interchange. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Motorway is a term for both a type of Road and a classification or designation To see information about the M25 motorway under construction in Ireland, see N25 road. The M40 Motorway is a motorway in the English Transport network that connects London to Birmingham. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. In Germany the standard design is to separate all turning traffic into a parallel lane so that the extra road space minimizes the problem of weaving. Collector-distributor roads are similar, but are separated from the main freeway lanes by a divider. Collector-distributor roads can be seen at the junction of Interstate 64 and Interstate 295 east of Richmond, Virginia, USA. Interstate 64 (abbreviated I-64) is an Interstate Highway in the eastern United States. Interstate 295 ( I-295) is an eastern and northern bypass of the cities of Richmond and Petersburg in the U This article is about the city of Richmond the capital of the Commonwealth of Virginia. The United States of America —commonly referred to as the Cloverleafs are often seen in urban highways within cities that grow out instead of up.
- A stack is a four-way interchange in which left turns are handled by semi-directional flyover ramps. A stack interchange is a free-flowing junction between two or more roads that allows turning in all directions In order to go left, vehicles first turn slightly right (on a 'right-turn' ramp), then go left on a ramp which goes over (or under) both freeways and connects to the 'right-turn' ramp in the opposite quadrant of the interchange. A stack interchange, then, has two pairs of left-turning ramps, which can be "stacked" in various configurations above or below the two through routes. Stacks do not suffer from the problem of weaving associated with cloverleafs, but require massive construction works. A basic stack involves roads on four levels, but in stacks including ramps for direct movement between high occupancy vehicle lanes, even more levels of stack can be needed; the interchange between Interstate 105 and Interstate 110 in Los Angeles County, California, is a five-level stack. In Transportation engineering and Transportation planning, a high-occupancy vehicle lane (or HOV lane) is a lane reserved for Vehicles with Interstate 105 (abbreviated I-105, and colloquially referred to as The 105 or the one-oh-five) is an interstate highway in southern Los Angeles County is a county in California and is by far the most populous county in the United States. This is not only expensive, but also unsightly, leading to considerable NIMBY opposition. NIMBY is an Acronym for Not In My Back Yard. The term is used to describe opposition to a new project by residents even if they themselves and those around Large stacks with multiple levels are sometimes referred to as Mixmasters or Spaghetti Bowls in the United States.
- In the late 1960s, there were parclo designs modified for freeway traffic. The ramps are longer to allow for higher speeds, and the loop ramp radii is larger as well. In a right-hand traffic (RHT) system, the signalized left turn is eliminated by an underpass or overpass. Right-hand traffic and left-hand traffic mean regulations requiring all traffic to keep either to the left or the right side of the Road. This includes the Highway 401-404 junction, and the former interchange between I-635 and US-75, the latter which has since been replaced by a five-level stack. Highway 404 is a 400-Series Highway in Ontario, Canada. It runs from the junction of Highway 401 and the Don Valley Parkway in The High Five Interchange is a large Freeway interchange that connects LBJ Freeway ( Interstate 635) and Central Expressway ( US 75) Interstate 635 or the Lyndon B Johnson Freeway (abbreviated I-635 or locally LBJ) is a partial loop around Dallas, Texas ( USA NCX redirects here For the transport protein see Sodium-calcium exchanger. The High Five Interchange is a large Freeway interchange that connects LBJ Freeway ( Interstate 635) and Central Expressway ( US 75)
- Another alternative to the stack for four-way junctions is the turbine interchange (known as a "whirlpool" in the UK). The turbine/whirlpool requires fewer levels while retaining semi-directional ramps throughout and has the left-turning ramps sweep around the center of the interchange in a spiral pattern. In Mathematics, a spiral is a Curve which emanates from a central point getting progressively farther away as it revolves around the point This has slightly less capacity because the ramps turn and change height more quickly. One example of a half-turbine-half-stack interchange is the Interstate 696/Mound Road interchange in Warren, Michigan, USA. Interstate 696 (I-696 is an interstate highway entirely within the U Mound Road is a 27 mile (45 km long principal Arterial road in the Metro Detroit area Warren is a city in Macomb County in the US state of Michigan. The United States of America —commonly referred to as the [1] Another example is the Interstate 95/U.S.Highway 6/Memorial Blvd. Route 84 (Rhode Island redirects here For the once-planned Interstate Highway, see Interstate 84 (Rhode Island. US Route 6, also called the Grand Army of the Republic Highway, is a main route of the U full turbine interchange in Providence, Rhode Island, USA. The United States of America —commonly referred to as the [2] A clearer example of a turbine interchange (without left-side ramps) is at the junction of Interstate 4 and Interstate 75 east of Tampa, Florida, USA. Interstate 4 (I-4 is a 13230-mile (21291 km intrastate Interstate Highway located entirely within the state of Florida, United States. Interstate 75 (I-75 is a major north-south Interstate Highway in the midwest and southeastern United States. The United States of America —commonly referred to as the [3]
Yet another example is the junction of Interstate 787 and US 9/US 20 in Albany, New York. Interstate 787 (abbreviated I-787) is an Auxiliary Interstate Highway in the U US Route 9 is a north-south United States highway in the states of Delaware, New Jersey, and New York in the United States. US Route 20 is an east-west United States highway. As the "0" in its route number implies U Albany is the Capital of the State of New York and the County seat of Albany County. [4] The Highway 401-Allen Road interchange is a hybrid of the turbine and clover-stack, with some ramps dedicated to serving the adjacent Yorkdale Mall rather than freeway to freeway traffic. William R Allen Road, known more commonly as Allen Road, The Allen Expressway or simply The Allen is a short Expressway / Freeway This article is about the shopping centre for the subway station named after it see Yorkdale (TTC.
Three Way
- A trumpet is an interchange traditionally used where one freeway terminates at another freeway; it involves at least one loop ramp connecting traffic either entering or leaving the terminating freeway with the far lanes of the continuous freeway. These junctions are also useful for toll roads as they concentrate all entering and leaving traffic in a single stretch of road, where toll booths can be installed. A toll road, (also known as a tollway, turnpike, pike, or toll highway, especially if it is constructed to Freeway standards Double Trumpet interchanges can usually be found when a toll road meets another toll road or a freeway. A toll road, (also known as a tollway, turnpike, pike, or toll highway, especially if it is constructed to Freeway standards
- A Directional T provides for high-speed ramps in all directions at a three-way interchange. A semi-directional T does the same, but some of the splits and merges are switched to avoid ramps to and from the passing lane. A passing lane is the lane on a multi-lane Highway or Motorway closest to the center of the road (the Central reservation)
- Hybrids, variations and rare types
Between a freeway and a non-freeway road
- Diamond interchange
- Cloverleaf interchange
- Parclo interchange (partial cloverleaf—sometimes called a folded diamond when only four ramps, in two quadrants, are used)
- Single-point urban interchange
- Roundabout interchange —this uses a single roundabout or traffic circle which spans the freeway with two over/underpasses (either above or below the freeway). A diamond interchange is a common type of Road junction. Diamond interchanges are used where a Freeway crosses a minor road Overview Cloverleaf interchanges viewed from overhead or on maps resemble the leaves of a Four-leaf clover. The parclo interchange (a Portmanteau of partial cloverleaf interchange) is a modification of a Cloverleaf interchange. A single-point urban interchange ( SPUI, ˈspuːi or /ˈspjuːi/ also called a single-point interchange ( SPI) or single-point diamond interchange A roundabout interchange is an interchange between a Freeway and a minor road A roundabout is a type of Road junction at which Traffic enters a one-way stream around a central island A traffic circle is an intersection with a circular shape and usually a central island These are very common in the UK, Ireland and France, but almost unknown in the rest of Europe and the United States. Such junctions can be improved by adding a flyover for straight-through traffic on the non-freeway, creating a stacked roundabout.
- Dumbbell interchange —this is similar to a diamond except that it uses roundabouts rather than signals or stop signs where the ramps meet the non-freeway road.
- Inner diamond interchange — this type of interchange allows opposing left turns to proceed concurrently where the ramps meet the surface street due to all four ramps meeting at a single intersection either above or below the freeway median, just as if it were an intersection of two surface streets. However, all of the ramps enter and exit the freeway from the innermost passing lanes, creating the potential for confusion to people not familiar with the area. Examples in the U. S. include Interstate 290 in Chicago and Interstate 244 in Tulsa. Interstate 290 (abbreviated I-290) is a main Interstate freeway that runs west from the Chicago Loop. Chicago (ʃɪˈkɑːgoʊ is the largest City by population in the state of Illinois and the American Midwest of the United States. This article is about the Interstate in the US state of Oklahoma.
- Diverging diamond interchange —similar to a traditional diamond interchange, except that the directional lanes of the non-freeway road cross over each other on either side of the freeway, preventing left-turning movements from crossing traffic, and allowing two-phase traffic signals (which handle higher volume), as no signaled left turns are required. A diverging diamond interchange is a rare form of Diamond interchange in which the two directions of traffic on the non- Freeway road cross to the opposite side As of April, 2008, at least three are known to exist in the world; the Missouri Department of Transportation is proposing a second in the Kansas City area. [1][2]
See also
References
External links
- Kurumi.com U.S. interchanges directory
- Glossary - Part of the publication Highway Design Handbook for Older Drivers and Pedestrians by the Turner-Fairbank Highway Research Center branch of the U. A free-flow interchange is an interchange in which all roads are grade-separated, and where movement from one road to another does not require the driver to stop for Grade separation is the process of aligning a junction of two or more transport axes at different heights ( 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 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 An unused highway may reference a Highway or highway ramp that was partially or fully constructed but was unused or later closed S. Federal Highway Administration
- Detailed history of interchanges with diagrams, in German
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