View source for Rail speed limits in the United States

{{short description|Overview of rail speed limits in the United States of America}}
{{update|track examples|date=January 2015|cat=Rail transport articles in need of updating}}
[[File:Speed Restriction Signs (11343937544).jpg|thumb|right|A {{convert|45|mph|adj=on}} speed restriction sign at [[Metro-North Railroad]]'s [[Port Chester station]].]]

'''Rail speed limits in the United States''' are regulated by the [[Federal Railroad Administration]]. Railroads also implement their own limits and enforce speed limits. Speed restrictions are based on a number of factors including [[curvature]], [[Railway signaling|signaling]], [[Railway track#Maintenance|track condition]], and the presence of [[level crossing|grade crossings]]. Like [[Speed limits in the United States|road speed limits in the United States]], speed limits for [[railway track|tracks]] and [[trains]] are measured in [[miles per hour]] (mph).

==Signal speeds==
{{Expand section|any history from before 1980s|date=January 2011}}
Federal regulators set train speed limits based on the signaling systems in use.<ref>{{cite web | title = United States Code of Federal regulations Title 49 - transportation, subtitle b - other regulations relating to transportation, chapter ii - federal railroad administration, department of transportation, part 236 - rules, standards, and instructions governing the installation, inspection, maintenance, and repair of signal and train control systems, devices, and appliances | url = http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&sid=e3336df9eea4aced3db461fccf707192&rgn=div5&view=text&node=49:4.1.1.1.30&idno=49 | accessdate = 2013-12-04}}</ref> Passenger trains were limited to 59 mph (95 km/h) and freight trains to 49 mph (79 km/h) on tracks without block signals, known as "[[dark territory]]." Trains without an automatic cab signal, train stop, or train control system were not allowed to exceed 79 mph (127 km/h). This rule, issued in 1947 and effective by the end of 1951, was a response to a serious [[Naperville train disaster|1946 crash in Naperville, Illinois]], involving two trains.<ref>{{cite web|url=http://www.trains.com/trn/default.aspx?c=a&id=4424|title=Ask Trains from November 2008|date=December 23, 2008|publisher=Trains Magazine
|archive-url=https://web.archive.org/web/20100624120252/http://www.trains.com/trn/default.aspx?c=a&id=4424|archive-date=2010-06-24|url-status=dead|accessdate=December 29, 2009}}</ref><ref>{{cite web |url=https://groups.yahoo.com/group/steam_tech/message/54227 |title=Hiawatha dieselization |author=William Wendt |url-status=dead |archive-url=https://web.archive.org/web/20121103043524/http://groups.yahoo.com/group/steam_tech/message/54227?l=1 |archive-date=2012-11-03 |publisher=Yahoo Groups |date=July 30, 2007 |access-date=2023-12-06}}{{cbignore}}</ref><ref>{{cite book|author=John Gruber and Brian Solomon|title=The Milwaukee Road's Hiawathas|publisher=Voyageur Press|year=2006|isbn=978-0-7603-2395-3}}</ref>

Following a 1987 train collision in Maryland, freight trains in high-speed areas were required to have speed limiters that could forcibly slow trains, rather than just alerting the operator through in-cab signals. In the Maryland crash, the signal panel had been partially disabled, including a muted whistle and a missing light bulb.

In response to the 2008 Chatsworth train collision in California, a federal law required that positive train control (PTC) be implemented nationwide by 2015.<ref>U.S. Rail Safety Improvement Act of 2008, {{USPL|110|432}}, {{USStat|122|4848}}, {{USC|49|20101}}. Approved 2008-10-16.</ref> After several extensions, the Federal Railroad Administration (FRA) announced on December 29, 2020, that PTC was operating on all required freight and passenger rail routes.<ref>{{cite web|url=https://railroads.dot.gov/train-control/ptc/positive-train-control-ptc|title=Positive Train Control (PTC)|publisher=Federal Railroad Administration|date=2021-09-09|access-date=2022-11-30}}</ref> While PTC’s main purpose is to prevent collisions, it also allows higher speeds in some cases. Different PTC systems are used in various regions across the country.

==Track classes==
[[File:CTA speed limit sign.jpg|thumb|right|A {{convert|10|mph|adj=on}} speed restriction sign along the [[Chicago "L"]].]]
{{Expand section|date=January 2011}}
In the [[United States]], the [[Federal Railroad Administration]] has developed a system of classification for track quality.<ref>{{cite web
|url= https://www.fra.dot.gov/Elib/Document/3019
|title=Federal Railroad Administration - Track and Rail and Infrastructure Integrity Compliance Manual : Volume II - Chapter 1 - Track Safety Standards - Classes 1 through 5
|accessdate= 2016-01-05
|author= Federal Railroad Administration
|authorlink= 
|date= 2014-01-06
|format= PDF
|publisher= United States Government
|pages= 2.1.15,2.1.16
|doi= 
|archiveurl= https://web.archive.org/web/20161225234304/https://www.fra.dot.gov/Elib/Document/3019
|archivedate= 2016-12-25
|quote= 
}}</ref><ref>{{cite web
|url= https://www.fra.dot.gov/eLib/Document/3020
|title= Federal Railroad Administration - Track and Rail and Infrastructure - Integrity Compliance Manual, Federal Railroad Administration Track Safety Standards Compliance Manual, Chapter 6
|accessdate= 2016-01-05
|author= Federal Railroad Administration 
|authorlink= 
|date= 2014-01-05
|format= PDF
|publisher= United States Government
|pages= 2.2.13
|doi= 
|archiveurl= https://web.archive.org/web/20161225234401/http://www.fra.dot.gov/Elib/Document/3020
|archivedate= 2016-12-25
|quote= 
}}</ref> The class of a section of track determines the maximum possible running speed limits and the ability to run passenger trains.
{| class="wikitable"
! Track type !! [[Freight train]] !! Passenger !! Examples
|-
| Excepted<ref group="us">Only freight trains are allowed to operate on ''Excepted track'' and they may only run at speeds up to {{convert|10|mph|km/h|abbr=on}}. Also, no more than five cars loaded with [[hazardous material]] may be operated within any single train. Passenger trains (in revenue service) of any type are prohibited.</ref> || <{{convert|10|mph|km/h|abbr=on}} || ''not allowed''  ||
|-
| Class 1 || {{convert|10|mph|km/h|abbr=on}} || {{convert|15|mph|km/h|abbr=on}}  ||Much yard, branch line, short line, and industrial spur trackage falls into this category.
|-
| Class 2 || {{convert|25|mph|km/h|abbr=on}} || {{convert|30|mph|km/h|abbr=on}}  ||Branch lines, secondary main lines, many regional railroads, and some tourist operations frequently fall into this class. Examples include the [[Burlington Northern Santa Fe]] (BNSF) branch from [[Sioux Falls]] to [[Madison, South Dakota]]; [[Napa Valley Wine Train]]’s {{convert|18|mi|km|adj=on}} ex-[[Southern Pacific Railroad]] line between [[Napa, California|Napa]] and [[St. Helena, California]]; and the entire [[Strasburg Rail Road]], spanning {{convert|4+1/2|mi}} between [[Strasburg, Pennsylvania|Strasburg]] and [[Leaman Place, Pennsylvania]].<ref name="Track Classifications">{{cite web | url= https://www.trains.com/trn/train-basics/abcs-of-railroading/track-classifications/ | title= Track Classifications| date= 26 August 2019}}</ref>
|-
| Class 3 || {{convert|40|mph|km/h|abbr=on}} || {{convert|60|mph|km/h|abbr=on}}  ||BNSF between [[Spokane]] and [[Kettle Falls, Washington]]; and [[Canadian National]]’s Wisconsin Central line between [[Neenah, Wisconsin]] and [[Sault Ste. Marie, Michigan]].<ref name="Track Classifications"/>
|-
| Class 4<ref group="us">Most mainline track, especially that owned by major railroads is Class 4 track{{Citation needed|date=July 2008}}</ref> || {{convert|60|mph|km/h|abbr=on}} || {{convert|80|mph|km/h|abbr=on|0}}  || Chicago’s [[Metra]]; and New England Central’s entire main line.<ref name="Track Classifications"/>
|-
| Class 5<ref group="us">Class 5 track is operated by freight railroads where freight train speeds are over {{convert|60|mph|km/h|abbr=on}}. On parts of the BNSF Railway's [[Chicago]]–[[Los Angeles]] mainline (historically, the old Santa Fe mainline), ATS-equipped passenger trains such as Amtrak's [[Southwest Chief]] can operate at up to {{convert|90|mph|km/h|abbr=on|0}}. This is gradually being reduced as the train stop system is retired, but freight trains over 60 mph still require class 5 track.{{Citation needed|date=May 2008}}</ref> || {{convert|80|mph|km/h|abbr=on|0}} || {{convert|90|mph|km/h|abbr=on|0}} || [[Union Pacific]]'s (UP's) Geneva, Clinton, and Boone subdivisions in [[Iowa]] between East Missouri Valley (near [[Council Bluffs]]) to the Illinois border near [[Clinton, Iowa|Clinton]];<ref name="IowaSRP2021">{{cite report |author=[[Iowa DOT]] |title=Iowa State Rail Plan |url=https://iowadot.gov/iowainmotion/railplan/2017/IowaSRP2022.pdf#page=240 |publication-date=November 2021 |pages=A–32 to A–34 |access-date=March 6, 2024}}</ref> UP’s main line between Council Bluffs and [[North Platte, Nebraska]]; [[Amtrak]]/[[SCRRA|SCRRA's]] and [[North County Transit District|NCTD's]] [[Surf Line]] between [[Fullerton, California|Fullerton]] and [[San Diego, California]].<ref name="Track Classifications"/>
|-
| Class 6 || colspan="2" align="center" | {{convert|110|mph|km/h|abbr=on|0}} ||Parts of [[Amtrak]]’s ''[[Amtrak Hartford Line|Hartford Line]]'' between [[New Haven, Connecticut]] and [[Springfield, Massachusetts]];<ref name="HartfordLine">{{cite report |author=AECOM Technical Services, Inc. |publisher=[[Connecticut Department of Transportation]] |title=Connecticut State Rail Plan (2022-2026) |publication-date=September 2022 |url=https://portal.ct.gov/-/media/DOT/documents/dplansprojectsstudies/plans/State_Rail_Plan/CTStateRailPlan2022-2026.pdf#page=35 |page=2–6 |access-date=March 6, 2024}}</ref> most of Amtrak's ''[[Lincoln Service]]'' between [[Chicago, Illinois]] and [[St. Louis, Missouri]];<ref>{{cite web|url=https://www.cbsnews.com/chicago/news/amtrak-high-speed-service-chicago-st-louis/|title=Amtrak to begin running 110 mph trains from Chicago to St. Louis|date=26 June 2023|website=CBS News}}</ref> portions of Amtrak's ''[[Wolverine (Amtrak train)|Wolverine]]'' between Chicago and [[Pontiac, Michigan]]; and [[Brightline]] between [[West Palm Beach]] and [[Cocoa, Florida]].<ref name=":0">{{Cite web |title=Brightline Florida: A Model for Fast, Successful Trains |url=https://www.hsrail.org/brightline-florida/ |access-date=2023-12-13 |website=High Speed Rail Alliance |language=en}}</ref>
|-
| Class 7<ref group="us">Some of Amtrak's [[Northeast Corridor]] has Class 7 trackage.{{Citation needed|date=May 2008}}</ref> || colspan="2" align="center" | {{convert|125|mph|km/h|abbr=on|0}}  ||Most of Amtrak's [[Northeast Corridor]];<ref name="jgmes.com">{{cite web | url= http://www.jgmes.com/webstart/library/table_fra_track.htm | title= Track Classifications}}</ref> and Brightline between [[Orlando International Airport]] and Cocoa, FL.<ref name=":0" />
|-
| Class 8<ref group="us">Portions of the Northeast Corridor are the only Class 8 trackage in [[North America]] allowing for {{convert|135|mph|km/h|abbr=on}}  {{Citation needed|date=May 2008}}</ref> || colspan="2" align="center" | {{convert|160|mph|km/h|abbr=on|0}}||[[Texas Central Railway]]; 3 segments of the Northeast Corridor totaling {{convert|33.9|mi|km|abbr=on}} in [[Rhode Island]]/[[Massachusetts]]<ref name="jgmes.com"/> and an additional {{convert|16|mi|km|abbr=on}} in [[New Jersey]]; [[Brightline West]] will have Class 8 trackage on its {{convert|218|mi|km|abbr=on}} route between [[Rancho Cucamonga, California]] and [[Las Vegas, Nevada]], going at top speeds of {{convert|186|mph|km/h|abbr=on}}.
|-
| Class 9<ref group="us">There is currently no Class 9 [[High-speed rail in the United States|high-speed rail]] in the United States, although [[Amtrak]] is currently undertaking test runs on [[Acela]] trains at {{convert|165|mph|km/h|abbr=on}}. [[California High-Speed Rail]] is planned to run at speeds up to {{convert|220|mph|km/h|abbr=on|0}} and the [[Texas Central Railway]] is planned to run at {{convert|205|mph|km/h|abbr=on}}. In the future, [[Amtrak]] [[Avelia Liberty]] trains may operate along the Northeast Corridor at up to {{convert|186|mph|km/h|abbr=on}}.</ref> || colspan="2" align="center" | {{convert|220|mph|km/h|abbr=on|0}} || [[California High-Speed Rail]] between [[Merced]] and [[Bakersfield]].
|}

{{reflist|group=us}}

==Curves==
{{main|Cant (road/rail)}}
Assuming a suitably maintained track, maximum track speed through curves is limited by the "[[centrifugal force]]" which acts to overturn the train. To compensate for this force, the track is superelevated (the outer rail is raised higher than the inner rail). The speed at which the centrifugal force is perfectly offset by the tilt of the track is known as the balancing speed.  Maximum speed can be found using the following formula, which provides an allowance for trains to operate above the balancing speed:
:<math>V_{max}=\sqrt{\frac{E_a + E_u}{0.0007d}}</math>

where:
:<math>E_a</math> is the amount in inches that the outside rail is [[Cant (road/rail)|superelevated]] above the inside rail on a curve 
:<math>E_u</math> is the amount in inches of unbalanced superelevation
:<math>d</math> is the [[degree of curvature]] in degrees per {{convert|100|ft|m}}
:<math>V_{max}</math> is given in [[miles per hour]]

[[File:Rail track lubricator.jpg|thumb|right|Track lubrication on a reverse curve in an area prone to movement due to wet beds.]]

Normally, passenger trains run above the balancing speed, and the difference between the balancing superelevation for the speed and curvature and the actual superelevation on the curve is known as unbalanced superelevation. Track superelevation is usually limited to {{convert|6|in|mm}}, and is often lower on routes with slow heavy freight trains in order to reduce wear on the inner rail. Allowed unbalanced superelevation in the U.S. is restricted to {{convert|3|in|mm}}, though {{convert|6|in|mm|0}} is permissible by waiver. [[Tilting train]]s like the [[Acela]] operate with even higher unbalanced superelevation, by dynamically shifting the weight of the train.  The actual overturning speed of a train is much higher than the limits set by the speed formula, which is largely in place for passenger comfort. There is no hard maximum unbalanced superelevation for European railways, some of which have curves with over {{convert|11|in|mm}} of unbalanced superelevation to permit high-speed transportation.<ref>{{cite web|url=http://Zierke.com/shasta_route/pages/05curve-curve.html|title=Comparison of upgrades needs to recognize the difference in curve speeds|last=Zierke|first=Hans-Joachim |accessdate=2008-04-10}}</ref>

The allowed unbalanced superelevation will cause trains to run with normal flange contact.  The points of wheel-rail contact are influenced by the [[tire profile]] of the wheels. Allowance has to be made for the different speeds of trains. Slower trains will tend to make flange contact with the inner rail on curves, while faster trains will tend to ride outwards and make contact with the outer rail. Either contact causes [[wear and tear]] and may lead to derailment if speeds and superelevation are not within the permitted limits. Many high-speed lines do not permit the use of slower freight trains, particularly with heavier [[axle load]]s. In some cases, the wear or friction of flange contact on curves is reduced by the use of [[flange]] lubrication.

==See also==
{{Commons category|Speed limit railway signs in the United States}}

* [[Slow zone]]
* [[Rail regulations in Canada]]
* [[Railroad operations]]
* [[Railway signalling]]

==References==
{{Reflist|2}}

{{Speed limits in the United States}}

{{DEFAULTSORT:Speed Limits In The United States (Rail)}}
[[Category:Rail transport operations]]
[[Category:Rail infrastructure in the United States]]
[[Category:United States railroad regulation]]