Slippery rail
Slippery rail, or low railhead adhesion,
Low adhesion caused by weather
Railhead contamination caused by weather conditions can occur at any time of year.
The leaf fall season causes the most disruption to rail operations.
Winter can provide problems of low adhesion when snow and ice are deposited on running lines.[4] Just as with road vehicles, black ice can cause trains to encounter difficulty when starting away, or can initiate wheel slide during braking.
Even summer can have its problems. A light rain shower following a long period of dry weather can sometimes cause similar low adhesion conditions to those of leaf fall contamination.[7] As the water dries it mixes with oxide debris and creates a paste that separates the wheel and rail reducing adhesion.[8][9] Although the effect is only short term, its unpredictability can cause a significant incident to occur. A morning dew can have the same effect.[7][10][11]
Disc brakes add to the problem
Before about 1960, most railway vehicles used
Lack of lineside maintenance
A report by England's
In the steam locomotive era, trees and other lineside vegetation would be regularly cut back to reduce the risk of their being ignited by sparks from the locomotive. As the railways ceased to use steam traction, this maintenance was allowed to lapse, and the resulting extra growth increases the supply of leaves thereby exacerbating the problem.[14]
Low adhesion caused by crushed insects
There are many substances which can cause low adhesion when they are deposited on the railhead. In Victoria, Australia, train wheels crushing plagues of introduced Portuguese millipedes which were crossing the tracks, caused passenger rail operator V/Line to be penalised more than $700,000 for cancellations and poor punctuality in one quarter of 2001.[15] In 2009, railway tracks at Tallarook in central Victoria were also affected by a Portuguese millipede plague, causing several trains to be cancelled.[16] The crushing of Portuguese millipedes is suspected to have caused a crash between two trains at Clarkson near Perth, Western Australia, in September 2013.[16]
Slippery rails caused by caterpillars were reported in Queensland in 1938.[17] Crushed locusts affected train operations on the Otavi Mining and Railway Company in South-West Africa (modern Namibia) in 1924.
Effects
The loss of friction between wheels and rail results in loss of tractive force: the wheels begin to spin, and in some instances the train is unable to move. In braking, substantial loss of friction results in reduced braking force. Braking distances are considerably longer, and in extreme cases the wheels may even lock up, causing the train to slide. Modern
In extreme cases, the build-up of leaf material can electrically insulate the wheels from the rails, resulting in a failure of signalling equipment to detect the presence of the train.[4] Where the problem is severe, Track Circuit Actuators[19] fitted to trains can help alleviate the problem.
In the United Kingdom, it was estimated that the poor adhesion problems cost the rail industry GBP 355 million (USD 449 million) a year.[20]
Mitigation measures
Railhead treatment
Treatment 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 metal particles. The coating is applied from special trains[21] (colloquially referred to as "Sandite trains" after the original proprietary mixture applied) and in some cases locally by hand applicators.[22]
Lineside-fitted Traction gel applicators[23] which apply liquid to the railhead as a train passes are fitted at sites where significant low adhesion regularly occurs, such as on the approach to stations.
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. Another method is using a high voltage electrical spark or plasma to volatilize the deposited material, but this method has only been used experimentally, as it is hindered by high power consumption, noise and rail degradation.[2]
Lasers
Since 2018, LIRR has used laser technology provided by Laser Precision Solutions, to tackle the autumn slip slide issue, using two 25 mph (40 km/h) LaserTrains.[24]
Sanders
Locomotives and
Novel methods
There are a range of novel methods being trialed for cleaning contamination from the railhead. One method uses solid CO2 ("dry ice")[25] which is fired at the track through a nozzle, removing commination through surface cooling, kinetic energy and sublimation.[26] Other methods have been trialed include microwave plasma[27] and ultrasound.[28]
Wheel slide protection
Wheel slide protection (WSP) equipment is fitted to passenger trains to manage the behaviour of wheel sets in low adhesion conditions. When the train is braking, it behaves like the ABS system in cars by releasing the brake on any axle if it detects that it is locking up. WSP can also control the traction system to prevent wheel spin when applying power.
Driving technique
Where trains have difficulty stopping during low adhesion conditions, the greatest risk is of passing a signal at danger or 'over-running' a station. At these times, train drivers adopt 'defensive driving',[4] which involves braking earlier and more gently than usual. Also, less power is applied when starting trains.
Before each leaf-fall season, train companies may arrange low-adhesion training
Although this provides only an approximation of how a train will behave during low adhesion, it does ensure that the driver can recognize the onset of wheel slide and will know the correct actions to take when it occurs.
In the UK, some passenger train operating companies publish a special 'leaf fall' timetable[29] to allow for the additional time that lighter braking and acceleration take.
Communication
Any information about the location and severity of low adhesion conditions will give train drivers warning of problems. In the UK there are several sources;
- Regular blackspots, known as Areas of known low adhesion are published in the Route Knowledgewhich they are examined on.
- Lineside signs showing the start and end of known regular low adhesion areas are provided at some locations.
- Drivers are required by the Rulebook,[30] to report to the signaller immediately either, any low railhead adhesion at a location not published in the Sectional Appendix, or any exceptionally poor rail adhesion at locations which are published in the Sectional Appendix.
- After receiving a report of low adhesion conditions, the signaller will contact drivers of following trains by radio to warn them. If it is safe to do so, the signaller may tell a driver to carry out a controlled test stop.[31] That driver will then stop the train using the brake force appropriate to normal conditions for the weather and conditions at that time of year, and report back to the signaller.
Vegetation management
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 York 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.[6] During the same period on the Long Island Rail Road, nearly 25% of cars were out of service due to slippery rail.[32][33]
In the US,
Methods for dealing with slippery rail have included trimming trees, the release of
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.[36]
SEPTA Regional Rail's method of preventing slippery rail is the Gel Trains. These three trains spray a high-pressure mixture of Sandite on the rails; in the fall, the Gel Trains also clean the rails using the high-pressure water jet method ahead of the gel application. These trains consist of a pressure washer and gel dispenser mounted on a converted flatcar, and a tank car which carries water. They are pulled on one end by one of SEPTA's work diesels (or a diesel borrowed from a local shortline such as the West Chester Railroad), and controlled at the other end by a former LIRR "Power Pack" cab unit (one a former ALCO FA, the other a former EMD F7). However, as of 2015; The FA and F7 were retired and replaced by Comet 1 cab cars.[38][39]
United Kingdom
In the United Kingdom, a number of rail companies change their timings and publish special "leaf fall timetables".[29]
During autumn, a fleet of Railhead Treatment Trains (RHTT)[40] run across the network using high pressure water-jetting to clean the railhead. These trains are timetabled to run between scheduled daytime services as well as during the night when less rail activity can allow the railhead contamination to build up.
The cryptic nature of rail company explanations for slippery rail and related phenomena made the phrase "leaves on the line" a standing joke,[41] and, along with variants such as "the wrong type of snow", is seen by members of the public who are not familiar with the problem as an excuse for poor service.[42][43]
Particularly problematic local trees include the
A term current in 2003 for cutting down or cutting back trees near the lines was "lineside vegetation management".[44]
Netherlands
Slippery rail is also a problem in the Netherlands, addressed by Nederlandse Spoorwegen (NS) and ProRail.[45] To prevent wheel lock, on some routes trains are required to brake earlier and accelerate more slowly. Furthermore, some (passenger) trains are fitted with equipment to apply Sandite gel on the tracks.[46] In autumn 2016, nearly 90,000 litres (24,000 US gal) of this gel was applied on the Dutch railway network.[47] In the fall of 2014 a pilot, in collaboration with Delft University of Technology, to use lasers to remove contaminations was announced by NS and ProRail.[48]
See also
- Adhesion railway
- Sandbox (railways)
- Sandite
- Tram sanders
- Tribology
References
- ^ "Low Adhesion Mockery Sticks Despite the Facts". Rail.co.uk. Retrieved March 31, 2016.
- ^ ISSN 0043-1648.
- ISBN 978-1-4831-5728-3.
- ^ a b c d e 2012 Autumn & Winter Season (Drivers' Briefing). London, UK: First Capital Connect. September 2012.
- ^ a b c Holmes, Elizabeth (November 21, 2006). "Why your train is late when autumn leaves fall (free preview)". The Wall Street Journal online. Retrieved November 22, 2006.
- ^ a b c Halbfinger, Caren (November 21, 2006). "'Flat wheels' deflate train commuters". The Journal News. White Plains, New York. Archived from the original on September 30, 2007. Retrieved November 22, 2006.
- ^ a b Summer Weather (Drivers' Briefing). London, UK: First Capital Connect. May 2012.
- S2CID 140827487.
- S2CID 245330956.
- S2CID 55583850.
- ISSN 0043-1648.
- ^ Wolmar, Christian (February 20, 1995). "Disc brakes linked to rise in train "slides"". The Independent. London. Retrieved July 21, 2012.
- ^ Laffan, R. M. (May 22, 1851). "The fatal collision on the Sutton Tunnel" (PDF). Railways Archive. House of Commons. pp. 7, 9.
- ^ "Royal Forestry Society: Leaves on the Line". Archived from the original on July 13, 2013. Retrieved July 21, 2012.
- ^ Butler, Pip (April 29, 2002). "The millipedes which stop trains". The Age. Retrieved May 26, 2015.
- ^ a b "Millipedes suspected in Perth train crash". The Australian. September 3, 2013. Retrieved May 26, 2015.
- Townsville Daily Bulletin. Qld. October 24, 1938. p. 6. Retrieved October 8, 2012.
- ^ "Railway Group Standards - Railway Wheelsets" (PDF). RSSB. February 2010. Retrieved December 8, 2016.
- ^ "Improving track circuit actuation performance at the wheel/rail interface". RSSB. 2011. Retrieved December 6, 2016.
- ^ "Adhesion". www.rssb.co.uk. Retrieved April 26, 2022.
- ^ "Leaves on the line". Rail.co.uk. Retrieved December 8, 2016.
- ^ "Permaquip Sand & Gel Applicators". Permaquip. Retrieved December 8, 2016.
- ^ "Traction Gel Applicators". JSD Rail. Retrieved November 21, 2016.
- ^ "StackPath". www.masstransitmag.com. Retrieved November 3, 2021.
- ^ "Track cleaning tech could prevent rail delays". The Engineer. October 5, 2021. Retrieved March 25, 2022.
- S2CID 237701740.
- ISSN 2227-7080.
- ^ "The Adhesion Rail Riddle - Ensuring Trains Can Brake | Engineering | University of Southampton". www.southampton.ac.uk. Retrieved March 25, 2022.
- ^ a b "National Rail Enquiries - Leaf Fall Timetable Changes - Autumn 2021". www.nationalrail.co.uk. Retrieved April 26, 2022.
- ^ "Online Rulebook – Module TW1 – Section 28.1 Rail-head adhesion" (PDF). RSSB. Archived from the original (PDF) on September 29, 2011. Retrieved December 10, 2016.
- ^ "Online Rulebook – Module TW1 – Section 28.2 Arranging a controlled test stop" (PDF). RSSB. Archived from the original (PDF) on September 29, 2011. Retrieved December 10, 2016.
- ^ Aitchison, Gavin (November 21, 2006). "Leaves on line cause rail delays". The Press. York. Retrieved November 22, 2006.
- ^ "Commuters, expect train delays". WABC-TV. New York. November 22, 2006. Retrieved November 22, 2006.
- ^ "SEPTA". Archived from the original on November 9, 2006. Retrieved November 23, 2006.
- ^ "Lasers clear leaves on the line". Physicsweb. May 2, 2002. Retrieved January 22, 2007.
- ^ Silberstein, Judy (November 15, 2006). "Commuters Warned Of "Slippery Rail" Delay". Larchmont Gazette. New York State. Retrieved November 22, 2006.
- ^ "New Jersey Transit". www.njtransit.com. Retrieved November 16, 2019.
- ^ Almeida, John P. "SEPTA Gel Train with F7 622 Philadelphia PA November 12, 2006". Railfan Pictures of the Day. The Philadelphia Chapter of the National Railway Historical Society. Retrieved February 12, 2013.
- ^ Almeida, John P. "What do you use to rescue a SEPTA gel train? Another SEPTA gel train! October 16, 2008". Railfan Pictures of the Day. The Philadelphia Chapter of the National Railway Historical Society. Retrieved February 12, 2013.
- ^ "Railhead Treatment Trains". Rail. 1 October 2014. Retrieved 1 April 2016.
- ^ a b "Leaves on the Line". The Royal Forestry Society. Archived from the original on 17 January 2008.
- ^ Martin Wainwrightc (20 April 2004). "Wrong type of pressure halts new trains". The Guardian.
- ^ Jon Yuill (25 July 2003). "Going Loco – your bizarre train tales". BBC News.
- ^ a b John May (22 October 2003). "Get a Grip". The Guardian.
- ^ Article, International Railway Journal, October 2003
- ^ Archived at Ghostarchive and the Wayback Machine: "Sandite: slim recept tegen blad op het spoor". YouTube.
- ^ "Weg met die smurrie op spoor". ProRail. September 29, 2017.
- ^ "NS zet laser in". NRC Handelsblad. August 14, 2014.