View source for British Rail Class 950

{{Use dmy dates|date=January 2017}}
{{Use British English|date=January 2017}}
{{Refimprove|date=January 2016}}
{{Infobox train
| background         = #F7B500
| name               = British Rail Class 950
| image              = Network Rail Class 950, 950001, Upton railway station (geograph 3818330).jpg
| imagealt           = 
| imagesize          = 300px
| caption            = Class 950 at {{rws|Upton}}, [[Wirral Peninsula|Wirral]] in January 2014
| interiorimage      = 
| interiorimagealt   = 
| interiorcaption    = 
| service            = 
| manufacturer       = [[British Rail Engineering Limited]]
| ordernumber        = 
| factory            = [[Holgate Road carriage works|Holgate Road Works]], [[York]]
| family             = [[British Rail Sprinter|''Sprinter'']]
| replaced           = 
| yearconstruction   = 1987
| yearservice        = 
| refurbishment      = 
| yearscrapped       = 
| numberbuilt        = 1
| numberservice      = 1
| numberpreserved    = 
| numberscrapped     = 
| predecessor        = 
| successor          = 
| formation          = 2 cars: {{abbr|DM|Driver's cab, Motor car}}-DM
| diagram            = 
| code               = 
| fleetnumbers       = {{ubl|Unit: 950001|Vehicles: 999600 and 999601<ref name=P5-1>{{cite Q |Q112224435 |series=British Railways Pocket Book No.3 |first1=Peter |last1=Fox |first2=Barry |last2=Hughes |page=50-51}}</ref>}}
| owner              = 
| operator           = [[Network Rail]]
| depots             = [[Railway Technical Centre]] ([[Derby]])<ref name=P5-1 />
| carbody            = [[Steel]]<ref name=BRBDMU220>{{cite book |title=Vehicle Diagram Book No. 220 for Diesel Multiple Unit Trains (Railcars) |publisher=British Railways Board |location=Derby |year=1982 |at=DP238 & DP239 |via=Barrowmore MRG |url=http://www.barrowmoremrg.co.uk/BRBDocuments/Book220Issue.pdf |access-date=18 February 2016 |archive-date=21 January 2015 |archive-url=https://web.archive.org/web/20150121172516/http://barrowmoremrg.co.uk/BRBDocuments/Book220Issue.pdf |url-status=dead}}</ref>
| trainlength        = 
| carlength          = {{cvt|19.930|m|ftin}}<ref name=BRBDMU220/>
| width              = {{cvt|2.816|m|ftin}}<ref name=BRBDMU220/>
| height             = {{convert|3.774|m|ftin|abbr=on}}
| floorheight        = 
| wheeldiameter      = 
| wheelbase          = 
| maxspeed           = {{convert|75|mph|km/h|abbr=on}}
| weight             = 
| axleload           = 
| steep gradient     = 
| traction           = 
| engine             = 2 × [[Cummins]] NT855-R5 {{avoid wrap|(one per vehicle)<ref name=BRBDMU220/>}}
| enginetype         = [[Straight engine|Inline-6]] [[Four-stroke engine|4-stroke]] {{nowrap|[[turbo-diesel]]<ref name="NTA855"><!--MARINE ENGINE HAS SAME CONFIGURATION AND BLOCK, MAJOR DIFFERENCES ARE IN COOLING WHICH DON'T APPLY FOR THESE PARAMS-->{{cite book |title=Marine Engine General Data Sheet N/NT/NTA 855-M |id=DS-4962 |date=18 February 2002 |publisher=Cummins Engine Company |location=Columbus, Indiana |page=1 |url=https://mart.cummins.com/imagelibrary/data/assetfiles/0055783.pdf |access-date=7 December 2022 |archive-url=https://web.archive.org/web/20221207162525/https://mart.cummins.com/imagelibrary/data/assetfiles/0055783.pdf |archive-date=7 December 2022 |url-status=live}}</ref>}}
| displacement       = {{cvt|855|cuin|L|0|order=flip}} per engine<ref name="NTA855" />
| poweroutput        = {{Convert|213|kW|hp|abbr=on}} per engine
| tractiveeffort     = 
| transmission       = [[Voith]] T{{narrow no-break space}}211{{narrow no-break space}}r ([[Hydrokinetic transmission|hydrokinetic]])
| acceleration       = 
| deceleration       = 
| aux                = 
| powersupply        = 
| hvac               = 
| electricsystem     = 
| collectionmethod   = 
| uicclass           = 2′B′+B′2′
| bogies             = 
| minimum curve      = 
| brakes             = [[Electro-pneumatic brake system on British railway trains|Electro-pneumatic]] (tread)
| safety             = 
| coupling           = 
| multipleworking    = 
| light              = 
| gauge              = {{track gauge|sg|allk=on}}
| notes              = 
}}

The '''British Rail Class 950''' is a [[diesel multiple unit]] that was purpose-built by [[British Rail Engineering Limited]]'s [[Holgate Road carriage works]] for the [[British Rail Research Division]] for use as a track assessment unit. It is currently operated by [[Network Rail]].

==Description==
[[File:950001 at Severn Tunnel Junction, 999600, closeup.jpg|thumb|left|Cab of vehicle 999600, showing the video camera and laser measurement equipment.]]
It was built in 1987 using the same bodyshell as the [[British Rail Class 150|Class 150/1 ''Sprinters'']].<ref>{{cite magazine |title=Sprinter track recorder handed-over to BR |magazine=The Railway Magazine |issue=1041 |date=January 1988 |page=9}}</ref> It was originally classified as a Class 180,<ref name=P5-1/> but was reclassified into the departmental series{{when|date=July 2025}}. As part of the [[privatisation of British Rail]], it passed to [[Railtrack]] in 1994 and then [[Network Rail]] in 2002. The unit is formed of two driving motor vehicles, numbered 999600 and 999601.

==Current operations==
The unit is currently painted in a plain overall yellow livery with Network Rail branding. It mostly works on branch lines, where the track quality is not good enough for larger and heavier track assessment stock. It is able to operate over most railway lines around [[Great Britain]]. The unit is based at the [[Railway Technical Centre]] in [[Derby]].

==Future==
In December 2024, Network Rail announced that the unit would be withdrawn and disposed of, to be replaced by additional (modified) Class 153s.<ref>{{cite news |url=https://www.railmagazine.com/news/2024/12/18/network-rail-class-150-to-be-withdrawn-and-disposed-of |title=Network Rail Class 150 to be withdrawn and disposed of |date=20 December 2024 |access-date=8 January 2025 |url-access=registration}}</ref>

==Fleet details==
{| class="wikitable"
!Class
!Operator
!Qty.
!Year built
!Cars per unit
!Unit nos.
!Notes
|-
!950
|[[Network Rail]]
|align=center|1
|align=center|1987
|align=center|2
|align=center|950001
| Network Rail Test Train
|}

==References==
{{reflist}}

==External links==
{{Commons category inline|British Rail Class 950}}

{{Network Rail Departmental Multiple Unit Classes}}
{{British Rail Sprinter}}
{{British Rail DMU}}

[[Category:British Rail diesel multiple units|950]]
[[Category:Non-passenger multiple units]]
[[Category:Train-related introductions in 1987]]
[[Category:Track recording trains]]
[[Category:British Rail Departmental Units]]