Level junction
Encyclopedia
In U.S. railroad practice, a level junction (or in the United Kingdom
a flat crossing) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at grade
(i.e. on the level).
The cross-over structure is sometimes called a diamond junction or diamond crossing in reference to the diamond-shaped center. The two tracks need not necessarily be of the same gauge
.
A diamond crossing is also used as a component of a double junction
, like the one illustrated on the right.
The opposite of a level junction is a flying junction
, where individual tracks rise or fall to pass over or under other tracks.
signals
to prevent collisions.
Level junctions, particularly those of fine angles or near right angles, create derailment
risks and impose speed restrictions. The former can occur as the flanges of the wheels are momentarily unsupported and unguided and can slip through the gaps in the rails, and the latter because the assembly contains elements that can break or vibrate loose.
Level junctions are considered a maintenance issue by railroad companies as the inherent gaps tend to be hard on locomotive and rolling stock wheelsets. Switched diamonds partially solve these problems, but introduce new ones.
where the lines of one company cross the lines of another company, and there is no particular need for the lines to be connected for through traffic.
At Rochelle Railroad Park
, the double track UP
mainline crosses the double track BNSF
mainline forming four diamond crossings altogether at this location.
In the United Kingdom
, a notable example is Newark flat crossing where the East Coast Mainline and Lincoln
to Nottingham
line cross (both double track). This is the fastest flat-crossing UK, with trains travelling north-south allowed to cross the junction at 100 mph (160 km/h). Protection of the junction is controlled by signalling.
are examples of this problem. The New York City Subway
system mostly uses flying junctions, but in a few older parts of the system, flat crossings can still cause delays. Examples include the 142nd Street Junction
and the Myrtle Avenue
junction.
Level junctions are often found on tram
or streetcar networks where lines cross or split. The MBTA in Boston has two of these underground on the Green Line
, one where the E Line departs the central subway just west of Copley Station, and another where the C Line and D Line split west of Kenmore Station. While the latter crossing rarely causes delays, the former is at an intersection of four lines and cars often have to wait for others to pass at peak hours. Earlier such splits in Boston (such as the disused crossing west of Boylston Station) were built as flying junctions, but the two level splits were built as level junctions mostly to save money.
, Ratlam
and Sabarmati stations in India.
At Porthmadog
, in Wales
, there is a flat-crossing between the single track standard gauge
Cambrian Line
and the narrow-gauge Welsh Highland Railway
.
, Australia
, flat crossings between narrow gauge cane tramways and main lines are being replaced by drawbridge
s so that the rails of the main line are completely unbroken by gaps or weak spots: this allows the main line speeds to be raised.
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...
a flat crossing) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at grade
At-grade intersection
An at-grade intersection is a junction at which two or more transport axes cross at the same level .-Traffic management:With areas of high or fast traffic, an at-grade intersection normally requires a traffic control device such as a stop sign, traffic light or railway signal to manage conflicting...
(i.e. on the level).
The cross-over structure is sometimes called a diamond junction or diamond crossing in reference to the diamond-shaped center. The two tracks need not necessarily be of the same gauge
Rail gauge
Track gauge or rail gauge is the distance between the inner sides of the heads of the two load bearing rails that make up a single railway line. Sixty percent of the world's railways use a standard gauge of . Wider gauges are called broad gauge; smaller gauges, narrow gauge. Break-of-gauge refers...
.
A diamond crossing is also used as a component of a double junction
Double junction
A double junction is a railway junction where a double track railway splits into two double track lines. Usually, one line is the main line and carries traffic through the junction at normal speed, while the other track is a branch line that carries traffic through the junction at reduced speed.A...
, like the one illustrated on the right.
The opposite of a level junction is a flying junction
Flying junction
A flying junction or flyover is a railway junction at which one or more diverging or converging tracks in a multiple-track route cross other tracks on the route by bridge to avoid conflict with other train movements. A more technical term is "grade-separated junction"...
, where individual tracks rise or fall to pass over or under other tracks.
Risks
Conflicting routes must be controlled by interlockedInterlocking
In railway signalling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. The signalling appliances and tracks are sometimes collectively referred to as an interlocking plant...
signals
Railway signal
A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train/engine drivers. The driver interprets the signal's indication and acts accordingly...
to prevent collisions.
Level junctions, particularly those of fine angles or near right angles, create derailment
Derailment
A derailment is an accident on a railway or tramway in which a rail vehicle, or part or all of a train, leaves the tracks on which it is travelling, with consequent damage and in many cases injury and/or death....
risks and impose speed restrictions. The former can occur as the flanges of the wheels are momentarily unsupported and unguided and can slip through the gaps in the rails, and the latter because the assembly contains elements that can break or vibrate loose.
Level junctions are considered a maintenance issue by railroad companies as the inherent gaps tend to be hard on locomotive and rolling stock wheelsets. Switched diamonds partially solve these problems, but introduce new ones.
Examples
Flat crossings are particularly common in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
where the lines of one company cross the lines of another company, and there is no particular need for the lines to be connected for through traffic.
At Rochelle Railroad Park
Rochelle Railroad Park
The Rochelle Railroad Park is a city park located in Rochelle, Illinois, where railfans can safely view and photograph trains. The park is situated in the eastern quadrant of the diamond crossing between the Union Pacific Railroad and BNSF Railway mainlines between Chicago and points west.The...
, the double track UP
Union Pacific Railroad
The Union Pacific Railroad , headquartered in Omaha, Nebraska, is the largest railroad network in the United States. James R. Young is president, CEO and Chairman....
mainline crosses the double track BNSF
BNSF Railway
The BNSF Railway is a wholly owned subsidiary of Berkshire Hathaway Inc., and is headquartered in Fort Worth, Texas. It is one of seven North American Class I railroads and the second largest freight railroad network in North America, second only to the Union Pacific Railroad, its primary...
mainline forming four diamond crossings altogether at this location.
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...
, a notable example is Newark flat crossing where the East Coast Mainline and Lincoln
Lincoln, Lincolnshire
Lincoln is a cathedral city and county town of Lincolnshire, England.The non-metropolitan district of Lincoln has a population of 85,595; the 2001 census gave the entire area of Lincoln a population of 120,779....
to Nottingham
Nottingham
Nottingham is a city and unitary authority in the East Midlands of England. It is located in the ceremonial county of Nottinghamshire and represents one of eight members of the English Core Cities Group...
line cross (both double track). This is the fastest flat-crossing UK, with trains travelling north-south allowed to cross the junction at 100 mph (160 km/h). Protection of the junction is controlled by signalling.
Local transport
Flat crossings appear in some urban passenger rail systems, which can cause delays at peak hours as a train heading in one direction may have to wait for trains heading in another direction to clear the junction before it can cross. The junctions leading onto and off from the Loop of the Chicago 'L'Chicago 'L'
The L is the rapid transit system serving the city of Chicago and some of its surrounding suburbs. It is operated by the Chicago Transit Authority...
are examples of this problem. The New York City Subway
New York City Subway
The New York City Subway is a rapid transit system owned by the City of New York and leased to the New York City Transit Authority, a subsidiary agency of the Metropolitan Transportation Authority and also known as MTA New York City Transit...
system mostly uses flying junctions, but in a few older parts of the system, flat crossings can still cause delays. Examples include the 142nd Street Junction
142nd Street Junction
The 142nd Street Junction is an intersection on the New York City Subway where the IRT White Plains Road Line and IRT Lenox Avenue Line join at grade . South of the junction, there is a double crossover. Then, two tracks turnoff , and that is where the 2 train connects to the White Plains Road...
and the Myrtle Avenue
Myrtle Avenue (BMT Jamaica Line)
Myrtle Avenue is a two-level express station on the BMT Jamaica Line of the New York City Subway...
junction.
Level junctions are often found on tram
Tram
A tram is a passenger rail vehicle which runs on tracks along public urban streets and also sometimes on separate rights of way. It may also run between cities and/or towns , and/or partially grade separated even in the cities...
or streetcar networks where lines cross or split. The MBTA in Boston has two of these underground on the Green Line
Green Line (MBTA)
The Green Line is a streetcar system run by the Massachusetts Bay Transportation Authority in the Boston, Massachusetts area of the United States. It is the oldest line of Boston's subway, which is known locally as the 'T'. The Green Line runs underground downtown and on the surface in outlying...
, one where the E Line departs the central subway just west of Copley Station, and another where the C Line and D Line split west of Kenmore Station. While the latter crossing rarely causes delays, the former is at an intersection of four lines and cars often have to wait for others to pass at peak hours. Earlier such splits in Boston (such as the disused crossing west of Boylston Station) were built as flying junctions, but the two level splits were built as level junctions mostly to save money.
Different gauges
Diamond crossings between meter and broad gauge tracks are present at IndoreIndore
Indore is one of the major city in India, the largest city and commercial center of the state of Madhya Pradesh in central India. Indore is located 190 km west of the state capital Bhopal. According to the 2011 Indian census, Indore city has a population of 1,960,631...
, Ratlam
Ratlam
Ratlam , known historically as Ratnapuri, is a city in the Malwa region in Madhya Pradesh state of central India. The town of Ratlam lies 480 m above sea level. It is the administrative headquarters of Ratlam District....
and Sabarmati stations in India.
At Porthmadog
Porthmadog
Porthmadog , known locally as "Port", and historically rendered into English as Portmadoc, is a small coastal town and community in the Eifionydd area of Gwynedd, in Wales. Prior to the Local Government Act 1972 it was in the administrative county of Caernarfonshire. The town lies east of...
, in Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, there is a flat-crossing between the single track standard gauge
Standard gauge
The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...
Cambrian Line
Cambrian Line
The Cambrian Line is a railway from Shrewsbury to Welshpool, Aberystwyth and Pwllheli. The railway runs first through the central part of Wales and then along the coast of Cardigan Bay....
and the narrow-gauge Welsh Highland Railway
Welsh Highland Railway
The Welsh Highland Railway is a long restored narrow gauge heritage railway in North Wales, operating from Caernarfon to Porthmadog, and passing through a number of popular tourist destinations including Beddgelert and the Aberglaslyn Pass. At Porthmadog it connects with the Ffestiniog Railway...
.
Drawbridge crossing
In QueenslandQueensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, flat crossings between narrow gauge cane tramways and main lines are being replaced by drawbridge
Drawbridge
A drawbridge is a type of movable bridge typically associated with the entrance of a castle surrounded by a moat. The term is often used to describe all different types of movable bridges, like bascule bridges and lift bridges.-Castle drawbridges:...
s so that the rails of the main line are completely unbroken by gaps or weak spots: this allows the main line speeds to be raised.