Slippery rail
Encyclopedia
Slippery rail is a condition of railways (railroads)
caused by fallen moist leaves
that lie on and cling to the top surface of the rails of railway tracks. The condition results in significant loss of friction between train wheels and rails, and in extreme cases can render the track temporarily unusable. In Britain, the situation is colloquially referred to as "leaves on the line".
states, New England
, many parts of Europe including the United Kingdom, and Southern Ontario, Canada, where there is heavy leaf fall in the autumn, the problem can arise. Where the leaves fall across a railway route, some of the leaves fall on the railheads; and at the passage of the next train, they are heavily compressed into a slippery low-friction coating on the rail and on the wheel treads. If the climate is damp, the wet leaves adhere to the rail very effectively. The draught caused by the passage of the train causes nearby leaves to be caught up in air currents, and more leaves are deposited on the railhead.
The build-up of this material is incremental, and it is hard enough not to be quickly worn away by the ordinary passage of trains.
s came into increasing usage. Brake blocks applied to the wheel tread had some effect in cleaning (by abrasion) the compressed leaf material from the wheel tread. It is generally agreed that the advent of disc brakes made the effects of leaf fall worse.
In extreme cases also, the build-up of leaf material can electrically insulate the wheels from the rails, resulting in a dangerous failure of signalling equipment to detect the presence of the train.
In summary, the railway can quickly become inoperable, or incur serious and cumulative delay as trains are unable to maintain normal point-to-point timings.
In the United Kingdom, it was estimated that the autumn leaves problem cost the rail industry GBP 60 million (USD 115 million) a year.
Both of these processes are effective for a limited duration; the jetting method is ineffective as soon as the next leaf falls; the sand deposition method is more durable, although rainfall usually removes the deposited sand quickly.
Train handling is modified in areas and at times when leaf fall is expected; sharp acceleration and braking are avoided. In the UK a special, somewhat less congested, timetable is published and operated at these times.
Removal of deciduous trees at the lineside is a management method to control the problem; however, there is political resistance to this in populous areas.
or Boston
. In November 2006, it was blamed for roughly one-third of all Metro-North Railroad
's Hudson
and Harlem lines' passenger cars being taken out of service. During the same period on the Long Island Rail Road
, nearly 25% of cars were out of service due to slippery rail.
In the US, Amtrak
, the Massachusetts Bay Transportation Authority
, southeastern Pennsylvania
's SEPTA
, Chicago
's commuter rail service Metra
, and MARC
, which serves Baltimore and Washington, D.C.
, have all reported delays due to slippery rail.
Methods for dealing with slippery rail have included cutting back trees adjacent to rails, the release of sand
on the train wheels for traction
, high-pressure water blasting and, most expensively, the use of high-powered laser blasts to clear the rails of leaves.
Metro-North has designed a system dubbed "Waterworld," which is a large flat rail car that blasts the rails with high-pressure water jets as the car moves over it.
New Jersey Transit
has used a similar method, which has proven quite effective. The device it uses is called "Aqua-Track" which, while attached to a moving rail car, sprays water at a pressure of 100000 psi (689.5 MPa) directly on to the part of the rail where the leaves cling. Since this system was introduced in 2002, the delays due to wheelslip have been reduced by over 60%.
SEPTA too has a method of preventing slippery rail, the Gel train. This sprays a high-pressure mixture of sandite on the rails.
, a number of rail companies change their timings and publish special "leaf fall timetables".
The cryptic nature of rail company explanations for slippery rail and related phenomena has led to the phrase "leaves on the line" becoming a standing joke, and, along with variants such as "the wrong type of snow", is seen by members of the public who do not understand the problem as an excuse for poor service.
Particularly problematic local trees include the sycamore, lime
, sweet and horse chestnut, ash, and poplar, which regrow or coppice after cutting back, and have large, flat leaves, which stick to the line and cause severe slippery rail. Further traits that cause problems are being quick-growing, pioneering trees, or producing a substantial amount of leaves. Poplars are particularly troubling because they tend to shed limbs.
The current term for cutting down or cutting back trees near the lines is "lineside vegetation management".
.
s.
Rail transport
Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...
caused by fallen moist leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
that lie on and cling to the top surface of the rails of railway tracks. The condition results in significant loss of friction between train wheels and rails, and in extreme cases can render the track temporarily unusable. In Britain, the situation is colloquially referred to as "leaves on the line".
Causes
In heavily deciduous forested areas like the American Mid-AtlanticMid-Atlantic States
The Mid-Atlantic states, also called middle Atlantic states or simply the mid Atlantic, form a region of the United States generally located between New England and the South...
states, New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
, many parts of Europe including the United Kingdom, and Southern Ontario, Canada, where there is heavy leaf fall in the autumn, the problem can arise. Where the leaves fall across a railway route, some of the leaves fall on the railheads; and at the passage of the next train, they are heavily compressed into a slippery low-friction coating on the rail and on the wheel treads. If the climate is damp, the wet leaves adhere to the rail very effectively. The draught caused by the passage of the train causes nearby leaves to be caught up in air currents, and more leaves are deposited on the railhead.
The build-up of this material is incremental, and it is hard enough not to be quickly worn away by the ordinary passage of trains.
Disc brakes
Before about 1960, most railway vehicles used brake systems in which brake blocks applied pressure to the wheel treads. From that time, disc brakeDisc brake
The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while it is in motion.A brake disc is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon–carbon or ceramic matrix composites. This is connected to the wheel and/or...
s came into increasing usage. Brake blocks applied to the wheel tread had some effect in cleaning (by abrasion) the compressed leaf material from the wheel tread. It is generally agreed that the advent of disc brakes made the effects of leaf fall worse.
Effects
The loss of friction between wheels and rail results in loss of tractive force—the train cannot move forward and the wheels merely spin, uselessly. In braking, substantial loss of friction results in the braking becoming ineffective, with the wheels locking. (Modern traction and braking control systems modify these effects and are not elaborated here, but the end result is similar.) Locked wheels can self-grind "flats" on the steel tyres, especially if the wheels are still sliding when arriving at a non-greasy section of rail, e.g. one that has previously been sanded. These flats subsequently cause severe vibration and the wheels must be re-tyred at great expense.In extreme cases also, the build-up of leaf material can electrically insulate the wheels from the rails, resulting in a dangerous failure of signalling equipment to detect the presence of the train.
In summary, the railway can quickly become inoperable, or incur serious and cumulative delay as trains are unable to maintain normal point-to-point timings.
In the United Kingdom, it was estimated that the autumn leaves problem cost the rail industry GBP 60 million (USD 115 million) a year.
Mitigation measures
Railways' mitigation measures generally involve some system to jet or blast the accumulated deposit away, or to coat it with a high-friction material. Blasting is usually carried out with water jets, often in combination with mechanical scrubbing apparatus. The coating method usually involves depositing sand in a paste on to the rail; as the sand may exacerbate the risk of unwanted insulation, the sand mix sometimes contains ferrous particles. The coating is applied from special trains (colloquially referred to as "Sandite" trains after the original proprietary mixture applied) and in some cases locally by hand.Both of these processes are effective for a limited duration; the jetting method is ineffective as soon as the next leaf falls; the sand deposition method is more durable, although rainfall usually removes the deposited sand quickly.
Train handling is modified in areas and at times when leaf fall is expected; sharp acceleration and braking are avoided. In the UK a special, somewhat less congested, timetable is published and operated at these times.
Removal of deciduous trees at the lineside is a management method to control the problem; however, there is political resistance to this in populous areas.
North America
Slippery rail has created severe disruptions of rail service, particularly in major metropolitan areas such as New YorkNew York metropolitan area
The New York metropolitan area, also known as Greater New York, or the Tri-State area, is the region that composes of New York City and the surrounding region...
or Boston
Greater Boston
Greater Boston is the area of the Commonwealth of Massachusetts surrounding the city of Boston. Due to ambiguity in usage, the size of the area referred to can be anywhere between that of the metropolitan statistical area of Boston and that of the city's combined statistical area which includes...
. In November 2006, it was blamed for roughly one-third of all Metro-North Railroad
Metro-North Railroad
The Metro-North Commuter Railroad , trading as MTA Metro-North Railroad, or, more commonly, Metro-North, is a suburban commuter rail service that is run and managed by the Metropolitan Transportation Authority , an authority of New York State. It is the busiest commuter railroad in the United...
's Hudson
Hudson Line (Metro-North)
Metro-North Railroad's Hudson Line is a commuter rail line running north from New York City along the east shore of the Hudson River. Metro-North service ends at Poughkeepsie, with Amtrak's Empire Corridor trains continuing north to and beyond Albany...
and Harlem lines' passenger cars being taken out of service. During the same period on the Long Island Rail Road
Long Island Rail Road
The Long Island Rail Road or LIRR is a commuter rail system serving the length of Long Island, New York. It is the busiest commuter railroad in North America, serving about 81.5 million passengers each year. Established in 1834 and having operated continuously since then, it is the oldest US...
, nearly 25% of cars were out of service due to slippery rail.
In the US, Amtrak
Amtrak
The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...
, the Massachusetts Bay Transportation Authority
Massachusetts Bay Transportation Authority
The Massachusetts Bay Transportation Authority, often referred to as the MBTA or simply The T, is the public operator of most bus, subway, commuter rail and ferry systems in the greater Boston, Massachusetts, area. Officially a "body politic and corporate, and a political subdivision" of the...
, southeastern Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
's SEPTA
Southeastern Pennsylvania Transportation Authority
The Southeastern Pennsylvania Transportation Authority is a metropolitan transportation authority that operates various forms of public transit—bus, subway and elevated rail, commuter rail, light rail, and electric trolley bus—that serve 3.9 million people in and around Philadelphia,...
, Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
's commuter rail service Metra
Metra
Metra is the commuter rail division of the Illinois Regional Transportation Authority. The system serves Chicago and its metropolitan area through 240 stations on 11 different rail lines. Throughout the 21st century, Metra has been the second busiest commuter rail system in the United States by...
, and MARC
MARC Train
MARC , known prior to 1984 as Maryland Rail Commuter Service, is a regional rail system comprising three lines in the Baltimore-Washington Metropolitan Area. MARC is administered by the Maryland Transit Administration , a Maryland Department of Transportation agency, and is operated under contract...
, which serves Baltimore and Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
, have all reported delays due to slippery rail.
Methods for dealing with slippery rail have included cutting back trees adjacent to rails, the release of sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
on the train wheels for traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
, high-pressure water blasting and, most expensively, the use of high-powered laser blasts to clear the rails of leaves.
Metro-North has designed a system dubbed "Waterworld," which is a large flat rail car that blasts the rails with high-pressure water jets as the car moves over it.
New Jersey Transit
New Jersey Transit
The New Jersey Transit Corporation is a statewide public transportation system serving the United States state of New Jersey, and New York, Orange, and Rockland counties in New York State...
has used a similar method, which has proven quite effective. The device it uses is called "Aqua-Track" which, while attached to a moving rail car, sprays water at a pressure of 100000 psi (689.5 MPa) directly on to the part of the rail where the leaves cling. Since this system was introduced in 2002, the delays due to wheelslip have been reduced by over 60%.
SEPTA too has a method of preventing slippery rail, the Gel train. This sprays a high-pressure mixture of sandite on the rails.
United Kingdom
In the United KingdomUnited 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 number of rail companies change their timings and publish special "leaf fall timetables".
The cryptic nature of rail company explanations for slippery rail and related phenomena has led to the phrase "leaves on the line" becoming a standing joke, and, along with variants such as "the wrong type of snow", is seen by members of the public who do not understand the problem as an excuse for poor service.
Particularly problematic local trees include the sycamore, lime
Tilia
Tilia is a genus of about 30 species of trees native throughout most of the temperate Northern Hemisphere. The greatest species diversity is found in Asia, and the genus also occurs in Europe and eastern North America, but not western North America...
, sweet and horse chestnut, ash, and poplar, which regrow or coppice after cutting back, and have large, flat leaves, which stick to the line and cause severe slippery rail. Further traits that cause problems are being quick-growing, pioneering trees, or producing a substantial amount of leaves. Poplars are particularly troubling because they tend to shed limbs.
The current term for cutting down or cutting back trees near the lines is "lineside vegetation management".
Netherlands
Slippery rail is also a problem in the Netherlands, addressed by Nederlandse SpoorwegenNederlandse Spoorwegen
Nederlandse Spoorwegen , or NS, is the principal passenger railway operator in the Netherlands.Its trains operate over the tracks of the Dutch national railinfrastructure, operated by ProRail, which was split off from NS in 2003...
.
Locusts
The Otavi Mining and Railway Company had a problem with slippery rails caused by crushed locustLocust
Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...
s.