The New Measurement Train (NMT), nicknamed the Flying Banana, is a specialised train which operates in the United Kingdom to assess the condition of track so that engineers can determine where to work. It is a specially converted InterCity 125, consisting of two Class 43 power cars and five or six Mark 3 carriages. It can check the condition of most main lines and some secondary routes operating on a four weekly cycle. This cycle replaced its original 13-week cycle after the introduction of the Plain Line Pattern Recognition (PLPR) Design Patrolling Program.
History The NMT was formed in direct response to concern over gauge corner cracking following the October 2000 Hatfield rail crash."Doctor Yellow" Rail issue 469 3 September 2003 pages 40–45 In September 2002 work commenced on preparing ex Virgin CrossCountry Class 43 power cars 43013, 43014 and 43062 and two Mark 2 and three Mark 3 carriages from the Railway Technical Centre fleet."Railtrack's HST test train work starts" Rail issue 444 18 September 2002 page 21"Virgin hands back ten HST power cars" Rail issue 447 30 October 2002 page 55"Now Departmental High Speed Trains" The Railway Magazine issue 1219 November 2002 page 5"Modular buffet prototype joins NR" Rail issue 458 2 April 2003 page 59 Only two carriages carried testing equipment, the extra carriages being required for brake force purposes.
The NMT entered service on 9 May 2003."NR's yellow HST enters service" The Railway Magazine issue 1227 July 2003 page 9Intensive inspection at high speed Railway Gazette International 1 July 2003 The two Mark 2s were replaced in 2004 with ex Virgin CrossCountry Mark 3s."Mk2s to be replaced on New Measurement Train" The Railway Magazine issue 1243 November 2004 page 58"Replacement Mk 3 added to NR's New Measurement Train" Rail issue 502 8 December 2004 page 15 In August 2005 a further Mark 3 joined the fleet fitted with a pantograph."Network Rail introduces new NMT coach" Rail issue 519 3 August 2005 page 17"Sixth NMT coach" The Railway Magazine issue 1254 October 2005 page 68
In 2004/05, power cars 43067, 43154 and 43196 were added while the core fleet was upgraded."Change of plan for additional NR NMT power car" Rail issue 480 4 February 2004 page 63"NMT gains another 43" Rail issue 513 11 May 2005 page 27"NR takes sixth NMT power car" Rail issue 527 23 November 2005 page 22 Two had been placed in store by February 2006, 43196 was placed in store September 2006."NMT power cars stored" The Railway Magazine issue 1259 March 2006 page 79New Measurement Train The 125 Group
In 2009/10, 43013, 43014 and 43062 had their Paxman Valenta engines replaced with MTU engines by Brush Traction. Ex London North Eastern Railway powercars 43290 and 43299 were hired in 2021 while the regular powercars were overhauled.Network Rail Rail Express issue 298 March 2021 page 27
Operation In the Production Vehicle (PV), lasers, vertical and horizontal actuators, gyros and accelerometers measure the interaction of the vehicle passing over the track. Outputs from the measuring system include track gauge, alignment, twist and cant. Other systems on the roof of the Development Vehicle (DV) measure features such as overhead line height and stagger. On the West Coast Main Line, particular care has to be taken to ensure that clearances are maintained for the use of tilting trains. The train captures video footage from the front and rear power cars.
The DV's equipment includes a video-based system utilising image recognition to look for defects such as missing clips. The DV also houses a non-contact overhead line monitoring system, which utilises lasers to measure the position of the wires in relation to the rails the train is on. High-powered white lights and cameras also enable the wear of the contact wire to be monitored. The wear is measured as the width of a strip on the underside, where the pantographs come into contact and wear away the cable. If the original thickness of the cable is known, this can be converted into a percentage of remaining area, which in turn when related to a maximum allowable wear can give an estimate of the remaining life. On hazy nights, the measuring equipment produces a blue glow that is visible some distance away.Holly Phillips, "Mysterious blue glow traced to Flying Banana", BBC News, 21 February 2026
The track recording systems vehicle has banks of screens allowing the team of three operators to view a range of system outputs including track faults, train location and radio signal strength. One of the mess cars hosts a system for monitoring and commissioning of Network Rail's GSM-R network.
From January 2020, the NMT was allocated to Loram UK at the Railway Technical Centre (RTC), Derby where all vehicle maintenance and overhauls were carried out.Loram wins Network Rail measuring train maintenance contract International Railway Journal 9 January 2020 Maintenance of the recording equipment is also carried out at the RTC by Network Rail engineers.
Effective December 2025 a new contract was awarded to Colas Rail;Emma Holden, "Colas Rail to operate and maintain New Measurement Train fleet", Rail Advent, 17 November 2025 since then, all maintenance has been carried out by the Colas NMT technicians at UKRL's site in Leicester.
Models Hornby has released runs of 43013/14, in both the original and "improving your railway" liveries. Hornby has also released complementary MK3 trailers.
See also Doctor Yellow – high speed measurement trains in Japan SNCF TGV Iris 320 – high speed measurement train in France China Railway comprehensive inspection trains – high speed measurement trains in China
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