Diamond interchange
Encyclopedia
Grade separation
Grade separation is the method of aligning a junction of two or more transport axes at different heights so that they will not disrupt 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...
from the minor road, one crossing the other over a bridge
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
. Approaching the interchange
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...
from either direction, an off-ramp diverges only slightly 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 where the ramp
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...
s meet the road are treated as conventional intersection
Intersection (road)
An intersection is a road junction where two or more roads either meet or cross at grade . An intersection may be 3-way - a T junction or fork, 4-way - a crossroads, or 5-way or more...
s. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, where this form of interchange is very common, particularly in rural
Rural
Rural areas or the country or countryside are areas that are not urbanized, though when large areas are described, country towns and smaller cities will be included. They have a low population density, and typically much of the land is devoted to agriculture...
areas, traffic
Traffic
Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel...
on the off-ramp typically faces a stop sign
Stop sign
A Stop sign is a traffic sign to notify drivers that they must stop before proceeding.-Specifications:The Vienna Convention on Road Signs and Signals proposed standard stop sign diameters of 0.6, 0.9 or 1.2 metres. UK and New Zealand stop signs are 750, 900 or 1200 mm, according to sign...
at the minor road, while traffic turning onto the freeway is unrestricted.
Cloverleaf interchange
A cloverleaf interchange is a two-level interchange in which left turns, reverse direction in left-driving regions, are handled by ramp roads...
. 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 often feature additional traffic control measures such as traffic light
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...
s and extra lane
Lane
A lane is a part of the roadway within a road marked out for use by a single line of vehicles in such a way as to control and guide drivers for the purpose of reducing traffic conflicts. Most public roads have at least two lanes, one for traffic in each direction, separated by Lane markings...
s dedicated to turning traffic.
The ramp intersections may also be configured as a pair of roundabout
Roundabout
A roundabout is the name for a road junction in which traffic moves in one direction around a central island. The word dates from the early 20th century. Roundabouts are common in many countries around the world...
s to create a type of diamond interchange often called a dumbbell interchange. Because roundabouts can generally 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 type of interchange is common in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, and is becoming increasingly common in the United States. Examples of dumbbell interchanges within the United States are located on Interstate 35
Interstate 35
Interstate 35 is a north–south Interstate Highway in the central United States. I-35 stretches from Laredo, Texas, on the U.S.-Mexico border to Duluth, Minnesota, at Minnesota Highway 61 and 26th Avenue East. Many interstates used to have splits or spurs indicated with suffixed letters , but I-35...
in Medford, Minnesota
Medford, Minnesota
Medford is a city in Steele County, Minnesota, United States. The population was 1,239 at the 2010 census.-Geography:According to the United States Census Bureau, the city has a total area of , all land...
, on Interstate 70
Interstate 70
Interstate 70 is an Interstate Highway in the United States that runs from Interstate 15 near Cove Fort, Utah, to a Park and Ride near Baltimore, Maryland. It was the first Interstate Highway project in the United States. I-70 approximately traces the path of U.S. Route 40 east of the Rocky...
in Avon, Colorado
Avon, Colorado
Avon is a Home Rule Municipality that is the most populous town in Eagle County, Colorado, United States. The population was 5,561 at the 2000 census. Avon is the gateway to the Beaver Creek Resort which lies about two miles south of the town. It was the previous site of Vail Resorts before the...
, on Interstate 87
Interstate 87
Interstate 87 is a Interstate Highway located entirely within New York State in the United States of America. I-87 is the longest intrastate Interstate highway in the Interstate Highway System. Its southern end is at the Bronx approaches of the Robert F. Kennedy Bridge in New York City...
in Malta, New York
Malta, New York
Malta is a town in Saratoga County, New York, United States. The town is in the central part of the county and is south of Saratoga Springs. The population was 13,005 at the 2000 census.- History :The town was first settled before 1865....
, and on Interstate 17
Interstate 17
Interstate 17 , also known as the Black Canyon Freeway, is an intrastate Interstate Highway located entirely within the state of Arizona, United States. I-17's southern terminus lies within Phoenix, at Interstate 10, and its northern terminus is in Flagstaff, at Interstate 40...
at Happy Valley Road north of Phoenix, Arizona
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
.
Where HOV lanes are present for carpool
Carpool
Carpooling , is the sharing of car journeys so that more than one person travels in a car....
ing, the ramps of a diamond interchange may be folded to the inside lanes instead of the outside. In urban
Urban area
An urban area is characterized by higher population density and vast human features in comparison to areas surrounding it. Urban areas may be cities, towns or conurbations, but the term is not commonly extended to rural settlements such as villages and hamlets.Urban areas are created and further...
areas this saves some space as well as requiring only one intersection instead of the two one-way intersections, which in rural or suburban areas can be turned into a single-point urban interchange
Single-point urban interchange
A single-point urban interchange , also called a single-point interchange or single-point diamond interchange , is a type of highway interchange...
. This in turn reduces waiting time for motorists at traffic light
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...
s on the smaller road, which may be a large local thoroughfare
Thoroughfare
A thoroughfare is a place of transportation intended to connect one location to another. Highways, roads, and trails are examples of thoroughfares used by a variety of general traffic. On land a thoroughfare may refer to anything from a rough trail to multi-lane highway with grade separated...
with heavy traffic.
See also
- Diverging diamond interchangeDiverging diamond interchangeA 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 on both sides of the bridge at the freeway. It is unusual in that it requires traffic on the freeway overpass to briefly drive on the...
- Single-point urban interchangeSingle-point urban interchangeA single-point urban interchange , also called a single-point interchange or single-point diamond interchange , is a type of highway interchange...