Slippery rail

Slippery rail is an adverse condition of railroads caused by fallen moist leaves that lie on and cling to the top surface of the rails of railroad tracks. The condition can cause severe premature wear on railroad equipment, delay railroad traffic and force trains to travel at reduced speeds. The condition usually occurs in Autumn months in heavily forested areas like the American Mid-Atlantic states, New England and much of the United Kingdom.cite news |title= Why your train is late when autumn leaves fall (free preview) |url= http://online.wsj.com/google_login.html?url=http%3A%2F%2Fonline.wsj.com%2Farticle%2FSB116416401633830365.html%3Fmod%3Dgooglenews_wsj|first= Elizabeth |last= Holmes|date= November 21 2006 |publisher= The Wall Street Journal online|accessdate= 2006-11-22] cite news |title= 'Flat wheels' deflate train commuters |url= http://www.thejournalnews.com/apps/pbcs.dll/article?AID=/20061121/NEWS01/611210363/1029/NEWS13|first= Caren |last= Halbfinger|date=November 21 2006|publisher= The Journal News |accessdate= 2006-11-22]

Train wheels can slip when they come in contact with wet and oily leaves, a phenomenon known as wheel slip. This causes the train's sensors to signal that excessive speed is occurring, which in turn instigates the track brakes to perform an emergency stop. The excessive stopping creates flat spots on the wheels, meaning they and the rail cars they support need to be serviced. The stopping of the trains also causes delays which create a "domino effect" of delays on other trains on the line. The reduced number of passenger cars frequently means overcrowding on trains.cite news |title= Commuters Warned Of "Slippery Rail" Delay |url= http://www.larchmontgazette.com/2006/articles/20061114slipperytrain.html|first= Judy |last= Silberstein|date=November 15 2006|publisher= Larchmont Gazette |accessdate= 2006-11-22]

Trains which have brake pads that bear directly on the steel tire of the wheel suffer less from this problem as the application of the brake effectively cleans the wheel where it is contact with the rail. Consequently freight trains tend to be less susceptible to the effects of slippery rail. The same brakes used to be the norm on passenger trains but they have been phased out in favor of lighter trains which use disk brakes, and in the case of electric trains regenerative braking, and the tire surface is not cleaned.

Effects of slippery rail

Slippery rail has created severe disruptions of rail service, particularly in major metropolitan areas such as New York or Boston. In November 2006, it was attributed to roughly one-third of all Metro-North Railroad's Hudson and Harlem lines' passenger cars having to be taken out of service.cite news |title= 'Flat wheels' deflate train commuters |url= http://www.thejournalnews.com/apps/pbcs.dll/article?AID=/20061121/NEWS01/611210363/1029/NEWS13|first= Caren |last= Halbfinger|date=November 21 2006|publisher= The Journal News |accessdate= 2006-11-22] During the same period on the Long Island Rail Road, nearly 25% of the cars were out of service due to slippery rail.cite news |title= Commuters, expect train delays |url= http://abclocal.go.com/wabc/story?section=traffic&id=4784900|date=November 22 2006|publisher= WABC-TV |accessdate= 2006-11-22] cite news |title=Leaves on line cause rail delays |url= http://www.yorkpress.co.uk/news/yorknews/display.var.1032195.0.leaves_on_line_cause_rail_delays.php |publisher= York Press|first= Gavin| last= Aitchison|date=November 21 2006|accessdate= 2006-11-22]

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, have all reported delays of their services due to slippery rail.

In the United Kingdom, it is estimated that the autumn leaves problem costs the rail industry £60 million (US$115 million) a year.cite press release |title= Biggest Ever Campaign Unveiled for Autumn Leaf-Fall Battle|url= http://www.networkrailmediacentre.co.uk/Content/Detail.asp?ReleaseID=2377&NewsAreaID=2&SearchCategoryID=2|date=October 16 2006 |publisher= Network Rail (UK)|accessdate= 2006-11-22]

Combating 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. [cite web |url= http://physicsweb.org/articles/world/15/5/3|title= Lasers clear leaves on the line|accessdate=2007-01-22 |format= |work= Physicsweb]

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 they use is called "Aqua-Track" which, while attached to a moving rail car, sprays water at a pressure of 68.9MPa (10,000psi) directly onto the part of the rail where the leaves cling. Since implementing this system in 2002, the delays due to wheel slip have been reduced over 60%.

In the UK, Network Rail has used satellites to locate troublesome areas for quick responses from two-person 'leaf-busting' crews that, according to a National Rail press release, "use railhead scrubbers, sand sticks and Natrusolve, which dissolves the leaf mulch to tackle the dangerous substance.". Recently Network Rail has adopted the traditional UK railway approach to the problem which was used before the railtrack era. It has been chopping down the trees on railway land close to the tracks.

The problem is so bad on the London to Aylesbury Line, that operators Chiltern Railways and Metropolitan Line run their own sandite trains and have revised train timetables during autumn to account for the excessive braking and lower speed limits in the Chiltern Hills.

Locusts

The Otavi Mining and Railway Company#Locusts had a problem with slippery rail caused by crushed locusts.fact

See also

* Sandite
* Sandbox (railways)

References

External links

* [http://septa.com/travel_advisory/slipperyrail.html SEPTA's "Slippery Rail Season" advisory]