In the field of road transport, an interchange is a road junction that uses grade separation, one or more ramps, to permit traffic on at least one highway to pass through the junction without interruption from other crossing traffic streams. It differs from a standard intersection. Interchanges are always used when at least one road is a controlled-access highway or a limited-access divided highway, though they are sometimes used at junctions between surface streets. Note: The descriptions of interchanges apply to countries where vehicles drive on the right side of the road. For left-side driving, layout of the junctions is the only left/right is reversed. A freeway junction or highway interchange or motorway junction is a type of road junction linking one controlled-access highway to another, to other roads, or to a rest area or motorway service area. In the UK, most junctions are numbered sequentially. In the US, interchanges are either numbered by interchange number. A highway ramp or slip road is a short section of road that allows vehicles to enter or exit a controlled-access highway.
A directional ramp tends toward the desired direction of travel: A ramp that makes a left turn exits from the left side of the roadway. Left directional ramps are uncommon, as the left lane is reserved for high-speed through traffic. Ramps for a right turn are always right directional ramps. A non-directional ramp goes opposite to the desired direction of travel. Many loop ramps are non-directional. A semi-directional ramp exits in a direction opposite from the desired direction of travel turns toward the desired direction. Many flyover ramps are semi-directional. A U-turn ramp leaves the road in one direction, turns over or under it, rejoins in the opposite direction. Weaving is an undesirable situation where traffic veering right and left must cross paths within a limited distance, to merge with traffic on the through lane; the German Autobahn system has Autobahn-to-Autobahn interchanges of two types: a four-way interchange, the Autobahnkreuz, where two motorways cross. Some on-ramps have a ramp meter, a dedicated mid-ramp traffic light that controls the flow of entering vehicles.
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. A complete interchange between a freeway and another road requires at least four ramps. Complete interchanges between two freeways have at least eight ramps, as having fewer would reduce capacity and increase weaving. Using U-turns, the number for two freeways can be reduced to six, by making cars that want to turn left either pass by the other road first make a U-turn and turn right, or turn right first and make a U-turn. Depending on the interchange type and the connectivity offered other numbers of ramps may be used. For example, if a highway interchanges with a highway containing a collector/express system, additional ramps can be used to link the interchanging highway with the collector and express lanes respectively. For highways with high-occupancy vehicle lanes, ramps can be used to service these carriageways directly, thereby increasing the number of ramps used.
An incomplete interchange has at least one or more missing ramps that prevent access to at least one direction of another road in the junction from any other road in the junction. A cloverleaf interchange is a two-level, four-way interchange where all turns across opposing traffic are handled by non-directional loop ramps. Assuming right-handed traffic, to go left vehicles first cross over or under the target route bear right onto a curved ramp that turns 270 degrees, merging onto the target route from the right, crossing the route just departed; these loop ramps produce the namesake cloverleaf shape. Two major advantages of cloverleaves are that they require only one bridge which makes such junctions inexpensive as long as land is plentiful, that they do not require any traffic signals to operate. However, weaving is a major shortcoming of cloverleaves, as the four total offramps and onramps are present, merge on the main routes; the capacity of this design is comparatively low. Cloverleaves use a considerable area of land, are more found along older highways, in rural areas and within cities with low population densities.
A variant design separates all turning traffic into a parallel carriageway to minimize the problem of weaving. Collector and distributor roads are similar, but are separated from the main carriageway by a divider, such as a guard rail or Jersey barrier. A stack interchange is a four-way interchange whereby a semi-directional left turn and a directional right turn are both available. Access to both turns is provided by a single offramp. Assuming right-handed driving, in order to cross over incoming traffic and go left, vehicles first exit onto an off-ramp from the rightmost lane. After demerging from right-turning traffic, they complete their left turn by crossing both highways on a flyover ramp or underpass; the penultimate step is a merge with the right-turn on-ramp traffic from the opposite quadrant of the interchange. An onramp merges both streams o
A Jersey barrier, or Jersey wall, is a modular concrete or plastic barrier employed to separate lanes of traffic. It is designed to minimize vehicle damage in cases of incidental contact while still preventing vehicle crossovers resulting in a head-on collision. Jersey barriers are used to reroute traffic and protect pedestrians and workers during highway construction, as well as temporary and semi-permanent protections against landborne attack such as suicide vehicle bombs. A Jersey barrier is known in the western United States as K-rail, a term borrowed from the California Department of Transportation specification for temporary concrete traffic barriers, or colloquially as a Jersey bump. Plastic water-filled barriers of the same general shape are now called Jersey barriers. Jersey barriers were developed in the 1950s, beginning in the U. S. state of New Jersey as separators between lanes of a highway. Over time, they became more modular. Taller barriers have the added advantage of blocking most oncoming headlights.
Although it is not clear when or where the first concrete median barriers were used, concrete median barriers were used in the mid-1940s on US-99 on the descent from the Tehachapi Mountains in the central valley south of Bakersfield, California. This first generation of concrete barriers was developed to minimize the number of out-of-control trucks penetrating the barrier, eliminate the need for costly and dangerous median barrier maintenance in high-accident locations with narrow medians – concerns that are as valid today as they were 50 years ago; the Jersey barrier called New Jersey wall, was developed in the 1950s, at the Stevens Institute of Technology, New Jersey, United States, under the direction of the New Jersey State Highway Department to divide multiple lanes on a highway. A typical Jersey barrier stands 32 inches tall and is made of steel-reinforced poured concrete or plastic. Many are constructed with the embedded steel reinforcement protruding from each end, allowing them to be incorporated into permanent emplacements when linked to one another by sections of fresh concrete poured on-site.
Their widespread use in road construction has led to wide application as a generic, portable barrier during construction projects and temporary rerouting of traffic into stopgap carpool and rush-hour reversing highway lanes. Most of the original barriers constructed in New Jersey in the 50s and early 60s were not "modular". Many of the first installations were much shorter than the heights discussed here about two feet tall; some dividers on county or local roads may have been lower than that since they replaced a raised concrete rumble strip that would dissuade but not prevent traffic crossing from one lane to another. Route 46 had the rumble strip in many places before the higher barrier was installed; these lower dividers are visible in old photographs. When the Bergen Mall was first opened in Paramus, these rumble strip dividers were extensively used on the roadway that separated the grocery stores from the mall proper; the design of the Jersey barrier was intended to minimize damage in incidental accidents and reduce the likelihood of a car crossing into oncoming lanes in the event of a collision.
In common shallow-angle hits, sheet-metal damage is minimized by allowing the vehicle tires to ride up on the lower sloped face. Head-on vehicle collisions are minimized by lifting the vehicle and pivoting it away from oncoming vehicles and back into traffic heading in its original direction. Modern variations include the F-shape barrier; the F-shape is similar to the Jersey barrier in appearance, but is taller, with somewhat different angles. The UK equivalent is the concrete step barrier. First tested in 1968 by the Department of Highways in Ontario, the Ontario Tall Wall is a variant of the Jersey barrier. Standing at 42 inches, it is 10 inches taller than the standard Jersey barrier. In Ontario, the Ministry of Transportation is replacing guiderails with these barriers on 400-series highways; the New Jersey Turnpike Authority developed and tested a similar, but reinforced, design. This barrier design has been credited with containing and redirecting larger vehicles, including semi-trailer trucks.
The states of New York and New Jersey have adopted the taller barrier for their roads, as compared to the standard 32 inches suggested by the Federal Highway Administration. Designs with two rectangular notches at the bottom allow for forklift-style lifting by front-end loaders. Barriers meant for short-term placement in military and security barrier uses, might include steel rebar loops embedded in the top surface for rapid hook-and-cable system lifting; the 2010 G-20 Toronto summit used modified modular Jersey barriers with wired fencing bolted onto the concrete. The fence used the barrier as sturdy base to prevent protesters from toppling the fence around the security zone at the Metro Toronto Convention Centre; the U. S. military nicknamed the devices as "Qaddafi Blocks" after truck bomb attacks in Beirut in 1983 resulted in more widespread use in military installations. Sometimes they are deployed to form a chicane to slow vehicular traffic arriving at military installations or other secure areas.
In the Philippines, jersey barriers were used for security and crowd control along the route of the papal co
Maryland State Highway Administration
The Maryland State Highway Administration is the state sub-agency responsible for maintaining Maryland's numbered highways outside Baltimore City. Formed under authority of the General Assembly of Maryland in 1908 as the State Roads Commission, under the direction of the executive branch of state government headed by the Governor of Maryland, it is tasked with maintaining non-tolled/free bridges throughout the State, removing snow from the state's major thoroughfares, administering the State's "adopt-a-highway" program, both developing and maintaining the State's freeway/expressway system. Since the reorganization of the several commissions, bureaus and assorted minor agencies with departments of the executive branch and establishment of the Governor's Cabinet in the early 1970s following the adoption of several individual reorganization recommendations after the rejection by the voters in a November 1968 referendum of the 1968 proposed overall new state constitution prepared by the 1967-1968 Constitutional Convention.
It is now a division of the larger establishment of the Maryland Department of Transportation and is overseen by an administrator. The headquarters for MSHA is located in Baltimore City; this building houses numerous divisions and offices, such as: Office of Planning and Preliminary Engineering Office of Highway Development Office of Traffic and Safety Office of Structures Office of Environmental Design Office of Construction Office of Policy and Research Office of Real Estate Office of CHART and ITS Development MSHA maintains four research labs located throughout the State, as well as the Office of Traffic and Safety located in Hanover—which houses several additional divisions. Some other services provided at the OOTS complex include: Traffic Engineering Design Division, responsible for the development of new traffic signals, signal modifications and signal phasing. Office of Maintenance, which provides assistance with recurring maintenance tasks that require more intensive study—particularly roadway safety and resurfacing projects.
The Statewide Operations Center is responsible for requesting incident response teams for incidents on State roadways. Responders may including police, medical, CHART, HazMat, MEMA, environmental, or maintenance teams; this facility is equipped to operate as a Statewide Transportation Emergency Operations Center. The signal shop, which provides personnel and equipment for the maintenance and programming of signals along State roadways in every county except Montgomery County; the sign shop, which designs and fabricates signing for use throughout the entire state. The Office of Materials Technology which consists of the Executive Services area and eight Divisions: Field Explorations, Engineering Geology and Geotechnical, Asphalt Technology, Concrete Technology and Aggregate Technology, Structural Materials and Pavement Markings and Materials Management. All are crucial in the maintenance of current roadways as well as the development of new ones. While OOTS and the Districts oversee the installation, operation and removal of traffic signals along State roadways, Montgomery County differs in that it is responsible for the operation and maintenance of all signals within the County—even those along State roadways.
However, the Districts and OOTS still control decisions regarding the installation and removal of signals. A result of this agreement is that it relieves MdSHA of some of the additional resource cost of the regular duties with regards to signals. There are seven districts in the State; these districts at the least, have divisions for traffic, construction and utilities. Each district oversees several maintenance shops—typically one per county; the following is a table of the districts, counties within their jurisdiction, their respective headquarters. Maryland Roads portal MdSHA website CHART website
Contraflow lane reversal
Contraflow lane reversal is the altering of the normal flow of traffic on a controlled-access highway, to either aid in an emergency evacuation or, as part of routine maintenance activities, to facilitate widening or reconstruction of one of the highway's carriageways. The term is used to refer to reversal of lanes which are configured for travel in one direction. In an emergency evacuation, contraflow lane reversal doubles the number of lanes available for evacuation traffic. Crossover sections are used to move outgoing traffic to these lanes. All incoming traffic is blocked until the end of the evacuation. Contraflow lane reversal is done on freeways and other controlled-access roadways. Use of contraflow lane reversal is considered to be an emergency measure, as the contraflow lanes lack proper signage and other traffic control devices needed to orderly conduct traffic in the opposite direction. A significant number of police officers or other officials are needed to manually direct traffic during a lane reversal.
From the 1990s, many states in the Southeastern United States adopted hurricane evacuation routes from coastal areas using contraflow lane reversals on Interstate Highways. State highway departments have coordinated on plans for traffic direction with state highway patrol agencies, constructed highway median crossovers, installed signage for drivers and barriers and swing arms to inhibit wrong-way collisions. Most evacuation plans involve only a single state. Current contraflow evacuation plans exist for: Alabama Mobile via I-65 Florida Jacksonville, via I-10 Pensacola, via I-10 South Florida, via Florida's Turnpike and Alligator Alley Southwest Florida, via I-75 The Space Coast, via SR 528 Tampa Bay, via I-4 Georgia Savannah, via I-16 Louisiana Lafayette, via I-49 Lake Charles, via I-10 and I-210 New Orleans metropolitan area, via I-10, I-12, I-55, I-59, the Lake Pontchartrain Causeway Maryland Ocean City, via US 50 and Maryland Route 90 Massachusetts Cape Cod via US-6, Route 3, Route 28 Mississippi Mississippi Gulf Coast, via I-59 and US-49 New Orleans metropolitan area, via I-55 New Jersey Jersey Shore, via Route 47/Route 347, Garden State Parkway, Atlantic City Expressway, Route 72/Route 70, Route 35, Route 138/I-195 South CarolinaBeaufort, via U.
S. 21 Charleston, via I-26 Georgetown County, via U. S. 17 The Grand Strand, via U. S. 501 Hilton Head Island, via U. S. 278 TexasCorpus Christi, via I-37 Houston, via I-10, I-45, I-69, U. S. 290 Freeport, Surfside Beach, Lake Jackson via SH 288 and SH 36. Rio Grande Valley, via I-2 from Harlingen to McAllen, I-69E from Brownsville to Harlingen, I-69C from Pharr to Falfurrias Virginia The Hampton Roads area, via I-64 When roads are undergoing construction amid heavy traffic, one lane of traffic may be blocked and another lane reversed. Single track roads are closed during reconstruction. A construction worker or police officer directs traffic with a "Stop/Slow Paddle", a sign displaying "STOP" on one side and "SLOW" on the other; the sign is turned, the other side proceeds. Traffic signals are sometimes used during bridge construction or any situation in which a lane must be closed during times when construction crews are not at work. Other cases include treating the street as a temporary one-way street in areas in which several nearby parallel streets are available as a detour for the opposing side.
If road construction necessitates the complete closure of one half of a road with four or more lanes, two lanes of traffic may be shifted to the other roadway. If the road being constructed is a highway, the used half is called a semi-highway; when controlled-access highways undergo reconstruction, both sides are reduced to one lane. In some cases, traffic may be shifted onto one half, making it a temporary two-lane freeway corridor. An example of this is Interstate 10 in Arizona, in which eastbound traffic is reduced to one lane and shifted onto the westbound half of the road. Another technique is to treat the rightmost hard shoulder as a travel lane. On a six-lane freeway, a third lane may be kept open for the busier direction, or the shoulder may be opened to allow for four lanes of traffic but with little or no shoulder space. In these situations, temporary "YIELD" or "STOP" signs are posted on merge ramps on freeways and uncontrolled roads with interchanges. In such cases, opposing directions are separated by jersey b
Partial cloverleaf interchange
A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange. The design has been well received, has since become one of the most popular freeway-to-arterial interchange designs in North America, it has been used in some European countries, such as Germany, Italy, the Netherlands, the United Kingdom. A diamond interchange has four ramps. A cloverleaf interchange has eight ramps; these are grade separated, unlike a parclo – traffic flows without stops on all ramps and throughways. A parclo has either four or six ramps. In Ontario, the specific variation is identified by a letter/number suffix after the name. Other jurisdictions do not have naming conventions, so Ontario's naming conventions are used in this article; the letter A designates that two ramps meet the freeway ahead of the arterial road, while B designates that two ramps meet the freeway beyond the crossing. The number designates. In left-hand drive countries, the ramps function the same as in right-hand drive countries, but ramps with the same designation appear visually reversed.
Common parclo configurations include the parclo A2, parclo B2 and parclo A4. Parclo A2 and B2 configurations contain four ramps. On each side of the freeway there is a directional ramp. In parclo A2, the loop ramps serve as the directional ramps serve as off-ramps. In parclo B2 the roles are reversed. Both on- and off-ramps require controlled intersections at the arterial road; the parclo A2 and B2 are used on rural freeways such as Highway 402 and Highway 416, where the ramps can be added without widening the street overpass/underpass to include deceleration lanes. The parclo A2 and B2 ramps are usually longer and allow for higher speeds than their A4 counterparts because of rural land availability, it is possible to upgrade an A2 to an A4 by adding directional ramps, serving arterial-to-freeway traffic that would otherwise be forced to make a left turn to enter the loop ramps. The parclo A4 contains six ramps. On each side on the freeway, there is an exit ramp, followed by a loop ramp and directional ramp entering the freeway.
The on-ramps are in the same configuration as a cloverleaf interchange, but there is one off-ramp for each freeway direction instead of two requiring a controlled intersection where the off-ramp meets the arterial road. The parclo A4 is one of the most popular designs, as all movements from the arterial road to the entrance ramps are made by right-hand turns, providing for a safer entrance to the freeway by eliminating left-hand turns into opposing traffic; this makes logical sense since freeways have a higher capacity than arterials and right-turn ramps serve to absorb capacity and reduce traffic on the arterial. Some parclos have the right-turning on-ramp leave the arterial road after the exit ramp intersection; this configuration is used when another road meets the freeway off-ramp and gives traffic from this road the option of turning right to use the directional on-ramp to enter the freeway. Traffic exiting the freeway to the arterial road is provided with a long straight exit ramp, preventing most speed-related rollovers.
These exit ramps are frequently multi-laned to accommodate traffic turning left, right, or going straight ahead in some cases. Traffic signals are installed at the end of the exit ramp to regulate the freeway traffic flowing onto the arterial; the parclo A4 is well-suited to suburban areas with high traffic levels. Ontario freeways throughout much of the southern portion of the province freeways in the Golden Horseshoe and Ottawa area, use the A4 parclo; these interchanges exist on some highways in the Montreal area. Caltrans favors this form for some recent projects, for example the reconstruction of I-880 and other highways in the San Francisco Bay Area and the Greater Los Angeles Area, they replaced previous full cloverleafs. All exiting traffic for both directions has a straight ramp and is controlled by a traffic light. Running off the road on an entering ramp is much less than on an exiting ramp. Metering lights are a common feature on the entering ramps; the junction of Saskatchewan Highway 1, Saskatchewan Highway 39 and Saskatchewan Highway 301 is an A4 parclo.
Highway 1 serves as the freeway. The parclo B4 interchange superficially appears to be a mirror image of the parclo A4. However, the B4 design provides freeway-to-arterial ramps without traffic lights, while traffic turning left from the arterial must cross opposing traffic. Although this design has the potential to flood the arterial with more freeway traffic than the parclo A4, one particular advantage is the ability to coordinate the traffic signals on the arterial in both directions independently; this is useful. The parclo B4 is less common in Ontario than the parclo A4, with the only examples being the following: Highway 402/Highway 40 interchange in Sarnia the interchange at Lauzon Parkway and the E. C. Row Expressway in Windsor Highway 17/Municipal Road 55 interchange in Sudbury Highway 406/St. David's Road interchange on the border of St. Catharines and Thorold Highway 400 and D
Berlin is a town in Worcester County, United States which includes its own historical Berlin Commercial District. The population was 4,485 at the 2010 census, has since grown in population, it is part of Maryland-Delaware Metropolitan Statistical Area. The town of Berlin had its start around the 1790s, part of the Burley Plantation, a 300-acre land grant dating back to 1677; the name Berlin is believed to be derived from a contraction of "Burleigh Inn", a tavern located at the crossroads of the Philadelphia Post Road and Sinepuxent Road. This may be why the traditional pronunciation of the town's name is BUR-lən, as opposed to the more modern pronunciations BAIR-lin and bair-LIN. Berlin incorporated as a town in 1868. In the early 20th century, Berlin was known as a rest stop for travelers on their way to the coastal resort of Ocean City, as well as a stop for tourists who enjoyed hunting and fishing on the lower Eastern Shore of Maryland. Just to the north of the town center of Berlin is Ocean Pines, Maryland, a waterfront census-designated place that shares the same ZIP code as Berlin.
Since the late 1980s, the town has undergone considerable revitalization of its historic downtown commercial district and adjacent residential areas. Berlin's historic residential areas feature nearly two centuries of architectural heritage from three distinct periods: Federal, 20th Century. Forty-seven of these structures have been noted in the National Register of Historic Places and the Berlin Commercial District. Berlin has been designated as a "Main Street Community" by the State of Maryland in recognition of its revitalization progress. In addition to the Berlin Commercial District, the Buckingham Archeological Site, Burley Manor, Caleb's Discovery, Fassitt House, Henry's Grove, Merry Sherwood and Williams Grove are listed on the National Register of Historic Places. Former U. S. Vice-President Spiro Agnew died at nearby Peninsula Regional Medical Center in Md.. Berlin is located at 38°20'N 75°13'W. According to the United States Census Bureau, the town has a total area of 3.15 square miles, all of it land.
As of the census of 2010, there were 4,485 people, 1,688 households, 1,155 families residing in the town. The population density was 1,423.8 inhabitants per square mile. There were 1,953 housing units at an average density of 620.0 per square mile. The racial makeup of the town was 68.8% White, 23.3% African American, 0.6% Native American, 1.4% Asian, 2.7% from other races, 3.3% from two or more races. Hispanic or Latino of any race were 5.5% of the population. There were 1,688 households of which 36.9% had children under the age of 18 living with them, 45.3% were married couples living together, 19.5% had a female householder with no husband present, 3.6% had a male householder with no wife present, 31.6% were non-families. 25.9% of all households were made up of individuals and 12.8% had someone living alone, 65 years of age or older. The average household size was 2.55 and the average family size was 3.07. The median age in the town was 38.4 years. 25.8% of residents were under the age of 18.
The gender makeup of the town was 45.5% male and 54.5% female. As of the census of 2000, there were 3,491 people, 1,347 households, 880 families residing in the town; the population density was 1,587.2 people per square mile. There were 1,427 housing units at an average density of 648.8 per square mile. The racial makeup of the town was 63.74% White, 32.03% African American, 0.20% Native American, 1.52% Asian, 0.03% Pacific Islander, 0.97% from other races, 1.52% from two or more races. Hispanic or Latino of any race were 3.38% of the population. There were 1,347 households out of which 34.1% had children under the age of 18 living with them, 40.2% were married couples living together, 21.0% had a female householder with no husband present, 34.6% were non-families. 29.7% of all households were made up of individuals and 18.3% had someone living alone, 65 years of age or older. The average household size was 2.46 and the average family size was 3.01. In the town, the population was spread out with 26.1% under the age of 18, 7.4% from 18 to 24, 26.2% from 25 to 44, 19.9% from 45 to 64, 20.4% who were 65 years of age or older.
The median age was 38 years. For every 100 females, there were 81.3 males. For every 100 females age 18 and over, there were 74.7 males. The median income for a household in the town was $33,438, the median income for a family was $36,653. Males had a median income of $29,946 versus $20,293 for females; the per capita income for the town was $19,303. About 12.9% of families and 14.3% of the population were below the poverty line, including 22.6% of those under age 18 and 12.5% of those age 65 or over. The town includes four public schools as well as one private school, which have 5,000 students combined. Worcester County Public Schools is one of the two top employers for the Town of Berlin. Buckingham Elementary School Berlin Intermediate School Stephen Decatur Middle School Stephen Decatur High School Worcester Preparatory School Berlin is located at the junction of east-west U. S. Route 50 and north-south U. S. Route 113, which meet at a cloverleaf interchange to the northeast of the town. US 50 bypasses the town to the north on the Ocean Gateway and heads west to Salisbury and east to Ocean City.
US 113 bypasses the town to the east on Worcester Highway and heads north to Selbyville and south toward Snow Hill and Pocomoke City. Maryland Route 818 runs north-south through the cen
A diamond interchange is a common type of road junction, used where a freeway crosses a minor road. The freeway itself is grade-separated from one crossing the other over a bridge. Approaching the interchange from either direction, an off-ramp diverges only from the freeway and runs directly across the minor road, becoming an on-ramp that returns to the freeway in similar fashion; the two places. In the United States, where this form of interchange is common in rural areas, traffic on the off-ramp faces a stop sign at the minor road, while traffic turning onto the freeway is unrestricted; the diamond interchange uses less space than most types of freeway interchange, avoids the interweaving traffic flows that occur in interchanges such as the cloverleaf. Thus, diamond interchanges are most effective in areas where traffic is light and a more expensive interchange type is not needed, but where traffic volumes are higher, the two intersections within the interchange feature additional traffic control measures such as traffic lights and extra lanes dedicated to turning traffic.
The at-grade variant of the diamond interchange is the split intersection. The ramp intersections may be configured as a pair of roundabouts to create a type of diamond interchange called a dumbbell interchange, sometimes called a double roundabout interchange; because roundabouts can handle traffic with fewer approach lanes than other intersection types, interchange construction costs can be reduced by eliminating the need for a wider bridge. This configuration allows other roads to form approach legs to the roundabouts and allows easy U-turns; this type of interchange is common in the United Kingdom and Ireland, is becoming common in the United States. Examples of dumbbell interchanges in the United States are located on Interstate 35 in Medford, Minnesota, on Interstate 87 in Malta, New York, on Interstate 17 at Happy Valley Road north of Phoenix, on Interstate 80 at California State Route 89 in Truckee, California. An example in Canada is found on the Pat Bay Highway in North Saanich, British Columbia, near Victoria International Airport.
One or both roundabouts in the dumbbell interchange may contain side lanes to increase the capacity. A good example of such a "turbo" dumbbell interchange, a half cloverleaf, can be seen in Jülich, Germany at 50.914055°N 6.323368°E / 50.914055. There are interchanges similar to dumbbells in which the ramps do not meet the roundabouts at intersections. One such interchange exists at the junction between the Ruta Interbalnearia and Route 35 North near La Floresta, Uruguay. A variation of the dumbbell interchange called a dogbone interchange, sometimes called a double roundabout interchange, occurs when the roundabouts do not form a complete circle but instead have a "raindrop" or "teardrop" shape; these two raindrop roundabouts are fused together. This configuration reduces conflicts between vehicles entering the raindrop roundabouts from the ramps, reducing queueing and delays, compared with the dumbbell interchange. Direct U-turns are not possible, although the movement can be made by circulating around both raindrop roundabouts.
An example of a dogbone interchange in the United States is located on Interstate 70 in Avon, Colorado. Several interchanges similar to those along Keystone Parkway are being built along the new US 31 freeway under construction in northern Indiana. There are some hybrid interchanges of dumbbell and dogbone having one raindrop and one full roundabout; this is made when the roundabout intersects more roads than ramps. Some examples are at exit 38 of the N7 road in Netherlands. A tennis ball interchange resembles a dogbone interchange, with the difference being that right turning movements cut through the roundabouts like a regular diamond interchange instead of going around the roundabout; such a design is found in Western Australia, between Roe Highway and Berkshire Road. A tight diamond interchange known as a compressed diamond interchange or a tight urban diamond interchange, is sometimes used in areas where there is insufficient right-of-way for a standard diamond interchange; the pair of intersections where the ramps meet the minor road are spaced.
This spacing forces the turn lanes for each direction to run beside each other, causing the minor road to be wider than it would be if it were a standard diamond. A single-point urban interchange is built with a large over- or clear underpass providing space for a single traffic signal controlled intersection with the ramps and the cross street. A contraflow left interchange is a modified TUDI, once installed at Lyons Road underneath Florida State Road 869, switching the left turn lanes on the cross street each other and bringing the long left turn phases from the single-point urban interchange to the tight urb