New Zealand DX class locomotive

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New Zealand DX class locomotive
DXB5143 at Platform 9 wgtn 1stJuly2008.jpg
DXB 5143, the first locomotive to be painted in the KiwiRail livery, stands at Wellington Railway Station Platform 9 on 1 July 2008.
Type and origin
Power type Diesel-Electric
Builder General Electric, United States
Model GE U26C
Build date 1972 - 1975
 • UIC Co-Co
Gauge 3 ft 6 in (1,067 mm)
Length 16.9 metres (55 ft 5 in)
Width 2.74 metres (9 ft 0 in)
Height 3.70 metres (12 ft 2 in)
Axle load DX 16.25 t (15.99 long tons; 17.91 short tons)
DXR 17.5 t (17.2 long tons; 19.3 short tons)
Adhesive weight DX 97.5 t (96.0 long tons; 107.5 short tons)
DXR 105 t (103 long tons; 116 short tons)
Loco weight DX 97.5 t (96.0 long tons; 107.5 short tons)
DXR 105 t (103 long tons; 116 short tons)
Prime mover General Electric 7FDL-12
RPM range 400 - 1050 rpm
Engine type V12 Diesel engine
Aspiration Turbocharged
Alternator General Electric GTA-11
Traction motors Six
Cylinders 12
Transmission 25/64 gear ratio
Performance figures
Maximum speed 105 km/h (65 mph)
Power output DX/DXB/DXC
2,050 kW (2,750 hp) original
2,240 kW (3,000 hp) uprated[1]
2,420 kW (3,250 hp)
Tractive effort DX 259 kN (58,000 lbf) continuous
Number in class 49
Numbers 2600 - 2648 (original)
5016 - 5520 (TMS)
DXR 8007, 8022
Nicknames "Dixies" (DX) "The Pig" (DXR 8007)[citation needed]
First run DX 1972
DXR 1993
DXC 1997
Disposition 46 in service
2 rebuilt as DXR
1 scrapped

The New Zealand DX class locomotive is a class of 49 Co-Co diesel-electric locomotives that currently operates on New Zealand's national railway network.

Built by General Electric in Erie, Pennsylvania, United States,[2] they were introduced to New Zealand between 1972 and 1976. The class is based on the General Electric U26C model, a narrow-gauge version of the GE U23C model. The U26C is also used in South Africa (see South African Class 34-900), Brazil, Kenya, Tanzania and Zambia.

The locomotives have seen several upgrades since their introduction and three versions now exist: the DXB, DXC and DXR.


The DX class was introduced in response to a requirement for a more powerful locomotive to handle traffic on the North Island Main Trunk (NIMT). Before their introduction the heaviest freight and passenger trains on the line required two members of the 1,060-kilowatt (1,420 hp) DA class to haul them. The DX class could haul heavier and faster trains than two DA's, even though they produced 70 kilowatts less than the combined DA's, as the single DX weighed 97.5 tonnes compared to the two DA's combined weight of 162 tonnes.

The first 15 members of the class (DX 2600 - DX 2614) were introduced in 1972. Initially, they were confined to the NIMT as their 16.25-tonne axle load was too heavy for many of the bridges on the other lines. As it was several bridges and viaducts on the NIMT had to be strengthened to take the weight of the locomotives.

There is no clear reason why the class was named the DX class. Diesel mainline locomotive classes begin with "D", followed by another letter - the mystery was why "X". Up to the DX class introduction, all classes had used letters A to J, and shunting locomotives used S. One possible explanation for the X was a reference to the 4-8-2 NZR X class steam locomotives, which ran on the central section of the NIMT between 1909 and 1957, and at the time of their introduction were the most powerful steam locomotives on NZR.

With bridges progressively strengthened throughout the North Island, and to further increase capacity on the NIMT in particular, 34 more members of the class were introduced in 1975 and 1976.

In service[edit]


DX 5310 and DQ 6324 on a freight train cross the Taylor River in Blenheim. Note the DXR-style long hood on 5310.

The DX class was initially used for heavy freight trains on the NIMT, especially on the central section where the power was needed. Most of the 49 class members in service by 1976 were used on this line, but a few also operated between Palmerston North and New Plymouth via the Marton - New Plymouth Line most days of the week, and also occasionally on passenger trains between Wellington and Masterton on the Wairarapa Line. In 1974 a DX ventured along the North Auckland Line as far north as Whangarei, and thereafter they saw occasional use in Northland in the late 1970s and early 1980s, but did not have any regular assignments there.

From introduction in 1972 a member of the class was assigned to haul the prestigious Silver Star overnight NIMT passenger express. Previously, the train required two DA class locomotives. The DX class was also used on the Northerner overnight passenger train when it was introduced in 1975.

In 1988 a major reshuffle of the mainline locomotive fleet took place nationwide as a result of the opening of the NIMT electrification and introduction of the EF class to handle the central section. For the DX class, this meant leaving the upper North Island, and being split into two fleets for service between Wellington and Gisborne/New Plymouth, and in the South Island. This was the first use of the class on the Palmerston North - Gisborne Line and the northern section of the Wairarapa Line between Masterton and Woodville.

In the mid-1990s, a small number of DXs returned to Auckland for use between Auckland and Tauranga via the East Coast Main Trunk, on the Kinleith Branch and regular service between Auckland and Whangarei. This was the first use of the class in regular service east of Hamilton. In 2000, a DX ventured north of Whangarei, which remains the last expansion phase of DX class territory.


Two DXC locomotives on a coal train from Ngakawau to Lyttelton crossing the Waimakariri River bridge

The DX class is still used primarily on heavy freight trains. The majority of the class now operate in the South Island, predominantly hauling coal trains between the West Coast mines and the port of Lyttelton near Christchurch. The trains consist of up to 30 CE class hopper wagons each holding 52 tonnes of coal, and require five members of the class to haul the train up the 3% (1 in 33) west-east grade of the Otira Tunnel,[3] and two members to haul it on the other sections of the line. These services are now exclusively hauled by the DXC sub-class. The class are also involved in general freight operations, and also employed periodically to haul the TranzAlpine and Coastal Pacific passenger trains.

In the North Island the DXB sub-class are the primary haulers of milk trains to Fonterra's Whareroa factory near Hawera on the MNPL, usually operating in pairs to haul these trains up the 1 in 35 Westmere Bank north of Wanganui. The class is also involved in other freight operations in the lower North Island, usually operating singly or in multiple with other locomotives.

A small number, including both DXRs, were based in the upper North Island, primarily in general freight use on the ECMT. With the allocation of the new DL class locomotives to that area, these locomotives were transferred to the South Island in late 2011.

The class are also periodically used to haul through trains on the central NIMT when EF locomotives are unavailable or the electrification requires maintenance. They are the primary haulers of the Capital Connection service between Palmerston North and Wellington.

In October 2013, KiwiRail reassigned six DXBs to the South Island due to the commissioning of the second batch of the DL class, leaving three assigned in the North Island.[4] All of these locomotives, including the units assigned to the South Island prior October 2013, were transferred back to the North Island to cover for the DL locomotives in March 2014, as the DL class were temporarily withdrawn from service after they tested positive for asbestos.[5] As of December 2017, nine DXBs have returned to the South Island, along with one of that were meant to be assigned in the North Island.


The DX class was originally numbered from DX 2600 to DX 2648 - which in common with NZR practice of the time was based on power output (2600 hp).

With the introduction of the computerised Traffic Monitoring System (TMS) in 1980, the class was renumbered. The DX class received four-digit numbers starting with 5, in which the fourth number is a check digit[2] for the number. The locomotives were numbered in order, with DX 2600 renumbered DX 5016 (6 being the check digit) and DX 2648 renumbered DX 5517. The numbers 500x, 515x, 534x and 549x were not used as these numbers do not generate a valid check digit, and DX 2639 never received a TMS number as it had been withdrawn by then.

The DXB and DXC sub-classes have kept their original TMS numbers, while the DXR class received new TMS numbers beginning with 8, numbered irrespective of their DX number. DX 5045 received a new TMS number using the DXB algorithim (5520) when it was upgraded and returned to service following being involved in a fatal derailment at Te Wera in 2002 (when re-introduced into service, the DXB classification was used to denote what is now the DXC sub-class).


DX 5483 in Cato Blue livery and DXC 5356 in Corn-cob livery

Upon introduction, all the DX class members were painted in "clockwork orange". The livery consisted of the locomotive body painted orange except for a yellow segment at the top of the locomotives - roughly the same shape and size as the orange segment on the original KiwiRail livery.

Between 1977 and 1986, the entire class was repainted in the International Orange "Fruit Salad" livery - red, grey, and yellow, which most of the class wore until the end of the decade. This livery had the road numbers displayed on the sides of the locomotives in large white numbers with DX 2612 the first to be painted as such. Since then, members of the DX class have received liveries including Cato Blue (Fruit Salad with blue instead of red), Bumble Bee (black and yellow), Corn-Cob (green and yellow) and the KiwiRail phase 1 and 2 schemes (grey, orange or red, and yellow). No DXs remain in the Fruit Salad, Cato Blue, Bumble Bee and Corn Cob liveries.


The locomotives received an upgrade during 1988 with the introduction of single-manning to improve visibility for the driver, with a large single front window replacing the original two small windows.

Fire suppression[edit]

Between 2013 and 2016, the DXC class were fitted with fire suppression to run the TranzAlpine through the 8.5-kilometre (5.3 mi) Otira Tunnel on the Midland Line due to a change in requirements resulting from the Commission of Inquiry in the Pike River Mine disaster, and as well on any other passenger trains on the Main North and Main South lines. Because of this, the number of Otira bankers have gone from three to five, which allows any loco without the system to be shut down. In mid 2016, the number of bankers were reduced from five to four. As of December 2016, all 32 units have been fitted with fire suppression.


DXC 5241 hauling a Christchurch to Picton mixed freight train at Oaro

There are two sub-classes of the DX - DXB and DXC.

The classifications DXB and DXC reflect modifications that have been carried out to the fleet. These include heavier drawgear, uprated engines, new cabs, (some have received DFT-style low hoods) and higher power traction motors.

The designation DXB denotes that the locomotive has been fitted with the Brightstar electronic traction control system, while DXC denotes that the locomotive has been additionally fitted with modified air intakes (“chutes”) as well as all the other upgrades including Brightstar. Thirteen of the original batch of 15 have been upgraded to DXB standard (DXC 5039, DX 5045, and DXC 5520 being the exceptions), and most of those from the subsequent batches upgraded to DXC standard - exceptions being DX 2639 (long since withdrawn from service).

Generally the DXC sub-class is assigned to the South Island, as the modified air intakes were designed to assist in are useful for working the Midland Line, coal trains (see above) particularly in the formerly electrified Otira Tunnel section, whereas the DXB sub-class were predominantly assigned to the North Island. Following the introduction of the first twenty DL class locomotives, four DXB's were reassigned to the South Island for general freight service on the Picton-Christchurch-Dunedin-Invercargill route, while DXC class locomotives have appeared in the North Island while on shakedown runs after overhaul.

The plain DX class is designated by GE as U26C, the newer upgrades are designated C26-MMI (2,750 hp DXB/DXC) and C30-MMI (3,250 hp DXB/DXC).

Rebuilds: DXR class[edit]

DXR 8007 with KiwiRail logo, 2009. Note the MkII "Universal Cab" as originally fitted to DXR 8022
DXR 8007 with KiwiRail logo, 2009. Note the MkII "Universal Cab" as originally fitted to DXR 8022
DXR 8022 and DXB 5143 at Ethelton with a container train from Picton to Christchurch

In 1993, New Zealand Rail Limited undertook a significant rebuilding of DX 5362 into the first of what was to be a new sub-class, the DXR. The DX had been stored out of service at Hutt Workshops since early in 1989 suffering a cracked frame, and therefore was an ideal candidate for the rebuilding programme. Work began to fit the locomotive with a new 3,300 hp GE 7-FDL diesel engine, upgraded traction motors with a ratio of 5.17 to the then-standard DX ratio of 4.55, and a new design of "Universal Cab" with a shorter low hood and more angular appearance. The use of 'R' (like the DBR class) denotes that the new locomotive was a rebuilt DX.

The newly rebuilt DX received the number DXR 8007 when it entered service in 1993 along with the prototype DFT class rebuild, DFT 7008. Initially it was intended that New Zealand Rail would rebuild all of the DX class locomotives to DXR specifications similar to the programme of rebuilding of the DF class into the DFT class, but after the privatisation of New Zealand Rail Limited (renamed Tranz Rail in 1995) later in 1993, the new management decided not to undertake further DX class rebuilds. One locomotive was however rebuilt to these original DXR specifications during the Tranz Rail years, DX 5310 in 2001 for its return to service following its derailment at Pukehou while hauling the Bay Express in 1995.[6] It did not though receive a new DXR style cab, so it retained its original DX classification until it was overhauled to DXC standards in 2010.

Following the purchase of Tranz Rail by Toll in 2003, the new management authorised the rebuild of DX 5235 - itself having been stored since being damaged in a collision in Christchurch in 2000 - which became DXR 8022. The new DXR featured minor differences in the carbody hood and a MkII version of the "Universal Cab" which was more boxy that the previous MkI variant as applied to DXR 8007. The new DXR rebuild was classified as DXR 8022 and entered service in late 2005. It was decided to rebuild DXR 8007 to match 8022 in the interests of standardisation, and so 8007 was again rebuilt at Hutt Workshops in 2006.

The two DXRs on the Waipara River Bridge with a freight train in November 2016

Upon each rebuild, GE classified 8022 (and reclassified 8007) as model C30-8Mi. In 2007, DXR 8022 was one of the locomotives involved in a biofuel trial using of a fuel mix of 5 per cent biodiesel and 95 per cent regular diesel over a period of six months.[7] With the introduction of the DL class locomotives into service the two DXR's were transferred to the South Island, and are now used between Middleton and Picton.

At 2,420 kilowatts (3,250 hp), the DXR class was the most powerful class of diesel-electric locomotive ever operated in New Zealand, until the introduction of the DL class in 2010, which surpassed the DXR's power output with 2,700 kilowatts (3,600 hp). As rebuilt by New Zealand Rail, DXR 8007 was classified by GE as their model C30-7M, while both 8007 and 8022 as rebuilt by Toll Rail are classified as model C30-8i.


As of 2017, only one DX class locomotive had been withdrawn from service. DX 2639 was involved in a crash south of the Parnell Tunnel near Newmarket station, at around 4:00pm on 23 March 1977. The locomotive was hauling a Wellington to Auckland express freight train when it crashed head-on into an Auckland to Helensville passenger train being hauled by DA 1426 that was on the wrong line. The cause was related to human error during a signalling failure. DX 2639 was subsequently written off and scrapped after less than a year in service.[8] In the early 1990s, a small group of DXs were withdrawn due to being surplus to requirements, but they were later returned to service.[9]

In August 2017, KiwiRail announced they were in discussions with global suppliers including General Electric, Electro-Motive Diesel, Alstom, CRRC and Stadler Rail to construct replacements for the remainder of the class. It is expected the first of the replacements to arrive in 2022/23.[10]

Class register[edit]

Key: In service On lease Out of service Preserved Overhaul or repair Scrapped
TMS No. Original No. Livery Introduced Withdrawn Status Allocated to Notes
DXB 5016 2600 KiwiRail Nov 1972 In service North Island
DXB 5022 2601 KiwiRail Nov 1972 In service South Island
DXC 5039 2602 KiwiRail Phase 1 Nov 1972 In service South Island
DXB 5051 2604 KiwiRail Nov 1972 In service North Island
DXB 5068 2605 KiwiRail Nov 1972 In service South Island Flat front short hood fitted
DXB 5074 2606 KiwiRail Nov 1972 In service North Island 2240 kW engine[11]
DXB 5080 2607 KiwiRail Nov 1972 In service South Island
DXB 5097 2608 KiwiRail Phase 1 Nov 1972 In service South Island
DXB 5108 2609 KiwiRail Nov 1972 In service North Island
DXB 5114 2610 KiwiRail Nov 1972 In service South Island
DXB 5120 2611 KiwiRail Nov 1972 In service South Island
DXB 5137 2612 KiwiRail Phase 1 Nov 1972 In service South Island Differs from other Phase 1 liveries with yellow cab sides and rear in place of grey
DXB 5143 2613 KiwiRail Phase 1 Nov 1972 In service South Island
DXB 5166 2614 KiwiRail Nov 1972 In service South Island
DXC 5172 2615 KiwiRail Dec 1975 In service South Island
DXC 5189 2616 KiwiRail Dec 1975 In service South Island
DXC 5195 2617 KiwiRail Dec 1975 In service South Island Flat front short hood fitted; derailed by a washout into the Rangitata River, January 2002
DXC 5206 2618 KiwiRail Dec 1975 In service South Island
DXC 5212 2619 KiwiRail Jan 1976 In service South Island
DXC 5229 2620 KiwiRail Feb 1976 In service South Island Flat front short hood fitted; collided head on with DX 5235 (Now DXR 8022) near Middleton Yard, December 2000
DXC 5241 2622 KiwiRail Jan 1976 In service South Island
DXC 5258 2623 KiwiRail Feb 1976 In service South Island
DXC 5264 2624 KiwiRail Feb 1976 In service South Island Flat front short hood fitted
DXC 5270 2625 KiwiRail Feb 1976 In service South Island
DXC 5287 2626 KiwiRail Feb 1976 In service South Island
DXC 5293 2627 KiwiRail Phase 1 Feb 1976 In service South Island
DXC 5304 2628 KiwiRail Feb 1976 In service South Island
DXC 5310 2629 KiwiRail March 1976 In service South Island Sustained major damage after derailing near Pukehou, November 1995. Took a 50 km/h curve at 90 km/h. Rebuilt with DXR style longhood.
DXC 5327 2630 KiwiRail Aug 1976 In service South Island Flat front short hood fitted. Collision with several coal wagons, Cass crossing station, November 2008. Substantial damage to left side of cab.
DXC 5333 2631 KiwiRail March 1976 In service South Island
DXC 5356 2632 KiwiRail September 1976 In service South Island
DXC 5379 2634 KiwiRail Apr 1976 In service South Island
DXC 5385 2635 KiwiRail Apr 1976 In service South Island
DXC 5391 2636 KiwiRail Apr 1976 In service South Island
DXC 5402 2637 KiwiRail September 1976 In service South Island
DXC 5419 2638 KiwiRail May 1976 In service South Island
2639 Clockwork Orange May 1976 March 23, 1977 Scrapped North Island Crashed near Newmarket,[8] scrapped September 1978[11]
DXC 5425 2640 KiwiRail May 1976 In service South Island Fitted with an anticlimber
DXC 5431 2641 KiwiRail Jul 1976 In service South Island Caught fire near Invercargill on 1 August 2014[12]
DXB 5448 2642 KiwiRail Jul 1976 In service South Island Involvement in a fatal collision at Waipahi in October 1999 with DFT 7254 (now DFB 7348) and DC 4202
DXC 5454 2643 KiwiRail May 1976 In service South Island
DXC 5460 2644 KiwiRail Jul 1976 In service South Island
DXC 5477 2645 KiwiRail Jun 1976 In service South Island
DXC 5483 2646 KiwiRail Jul 1976 In service South Island
DXC 5500 2647 KiwiRail Aug 1976 In service South Island
DXC 5517 2648 KiwiRail Aug 1976 In service South Island
DXC 5520 2603 KiwiRail Nov 1972 In service South Island Formerly DX 5045. Returning to service following fatal derailment at Te Wera in 2002. Flat front short hood fitted.
DXR 8007 2633 KiwiRail Apr 1976 Under overhaul South Island Formerly DX 5362. Rebuilt 1993 & 2006. General Electric model C30-8Mi. Under overhaul at Hutt Workshops.[13]
DXR 8022 2621 KiwiRail Jan 1976 In service South Island Formerly DX 5235. Rebuilt 2003. General Electric model C30-8Mi.

See also[edit]

References and citations[edit]


  1. ^ KiwiRail 2011, p. 21.
  2. ^ a b Sinclair, Roy (1992). Rail, the Great New Zealand Adventure. Grantham House Publishing. ISBN 9781869340131. 
  3. ^ "Friends in High Places". Off the Rails: A Love Story. Episode 4. 2005. TVNZ. TV One. 
  4. ^ "Railfan". 20 (1). Triple M Publications. December 2013. ISSN 1173-2229. 
  5. ^ "Railfan". 20 (1). Triple M Publications. March 2014. ISSN 1173-2229. 
  6. ^ "Australasian pics". 
  7. ^ "All Aboard for 'Bioloco' Ride". The Dominion Post. 2007-12-09. Retrieved 2008-10-09. 
  8. ^ a b Churchman, Geoffrey B (1992). Danger Ahead New Zealand Railway Accidents in the Modern Era. IPI Publishing Group. p. 92. ISBN 0-908876-74-2. 
  9. ^ "Railfan". 2 (4). Triple M Publications. September 1996. ISSN 1173-2229. 
  10. ^ "Railfan". 23 (4). Triple M Publications. September 2017. ISSN 1173-2229. 
  11. ^ a b David Parsons (2002). New Zealand Railway Motive Power 2002. New Zealand Railway and Locomotive Society. ISBN 0908573782. 
  12. ^ "Flickr picture showing DXC 5431 after fire". 
  13. ^ "Railfan". 24 (1). Triple M Publications. December 2017. ISSN 1173-2229. 


External links[edit]