NSB Class 73

NSB Class 73

Company type	Electric multiple unit train
Industry	Rail transport
Founded	1999
Founder	Norwegian State Railways (NSB)
Products	Electric multiple units
Parent	Norwegian State Railways (NSB)

NSB Class 73 () represents a fleet of 22 electric multiple units produced by Adtranz for the Norwegian State Railways. These four-car trainsets are adaptations of the Class 71, which itself is derived from the Swedish X2 model. The A-series consists of 16 intercity units delivered between 1999 and 2000, operating on the Bergen, Dovre, and Sørland Line routes; this service was marketed under the name Signatur until 2003. Meanwhile, the B-series includes six regional units introduced in 2002 for use on the Østfold Line, initially part of NSB’s Agenda initiative.

Each unit delivers a power output of , reaches a top speed of , spans in length, and accommodates 204 passengers in the A-series or 250 in the B-series. These trains incorporate an active tilting system that allows higher speeds when navigating curves.

The delivery of these trains was delayed, and upon introduction, they operated under exemptions from certain safety standards. On 17 June 2000, an axle failure caused a derailment near Nelaug Station, resulting in a suspension of service lasting one month. Investigations uncovered design shortcomings and inadequate maintenance procedures. After resuming operation, tilting functionality was disabled, restricting speeds to those comparable with older models. Structural reinforcements enabled reactivation of the tilting mechanism and increased speeds by 2004. A derailment on the Bergen Line in 2007 raised questions about performance in snowy conditions; however, assessments confirmed that axle loads were sufficient and that the train’s design reduced derailment impact relative to traditional trains. On 16 June 2011, two units were destroyed by fire inside a snow tunnel at Hallingskeid Station.

Specifications

The Class 73 is an electric multiple unit composed of four cars built by Adtranz, equipped with eight bogies—three of which are powered—producing a total output of . These trains feature active tilting technology that permits speed increases between 20 and 30 percent when negotiating curves on conventional rail lines. The maximum operational speed is . Each four-car set measures in length; A-series units weigh , while B-series units have a weight of . Constructed with steel bodies, these trains include pressurized driver cabins and rail brakes installed on all carrying bogies.

Passenger capacity differs between series: the A-series offers seating for 207 individuals, whereas the B-series seats up to 250 due to a more compact bistro area and denser seating arrangements. Interior design incorporates color-coded seats by car along with cherry wood accents. Seating classes are divided into standard and Komfort categories—the latter featuring leather upholstery and laptop power outlets. Dining options include hot meals served either at passengers’ seats or within the dining car, with menus that change according to time of day. Additional onboard facilities comprise a family play zone, accessibility features for handicapped passengers, bicycle storage, and starting from 2011, complimentary Wi-Fi service.

Background

During the early 1990s, NSB conducted evaluations on enhancing intercity rail services within Norway. It was determined that constructing dedicated high-speed rail infrastructure would require an investment of NOK 56 billion. As an alternative, tilting train technology was selected to increase speeds while utilizing existing tracks. The Gardermoen Line was engineered for maximum speeds up to , fulfilling a stringent requirement to enable a 19-minute journey time to Oslo Airport.

Although initial plans considered acquiring Swedish X2 trains to facilitate interoperability across Nordic countries, NSB ultimately abandoned this approach. In 1995, under director-general Osmund Ueland’s leadership, NSB shifted its strategy away from new rail construction towards adopting tilting train technology.

Both Class 71 and Class 73 trace their lineage back to the Swedish X2 model but incorporate enhancements such as distributing traction motors across all four cars instead of employing a separate locomotive unit—this improves traction capabilities and optimizes interior space usage. NSB conducted trials with X2 trains within Norway before commissioning Class 71 units in 1995 for the Airport Express Train service; options for additional intercity and regional train orders were included in this contract. The first option for intercity trains was exercised in 1997.

Class 73 distinguishes itself from Class 71 by featuring four cars instead of three, redesigned door configurations with fewer door sets per car, and implementation of active tilting technology. Deliveries commenced in the late 1990s backed by an initial investment totaling NOK 1.6 billion.

In April 1999, NSB launched the Signatur brand specifically for Class 73 intercity services, introducing Comfort and Comfort Plus seating classes alongside a blue-and-silver exterior livery. This premium offering aimed to reduce travel times supported by NOK 1.2 billion worth of infrastructure improvements carried out by the Norwegian National Rail Administration.

Tickets for Signatur services included a surcharge of NOK 25 compared to standard fares and were distributed through Amadeus CRS—a system previously exclusive to airlines operating within Norway. Prices ranged from NOK 250 to NOK 780 depending on travel class and timing, positioning this service as competitive with air travel on routes such as Oslo to Kristiansand by providing comparable city-center-to-city-center journey durations.

Entry into service

Just three days before the planned launch, the Norwegian Railway Inspectorate had yet to grant approval for the trains, citing several safety concerns: problems with wheels and axles; insufficient documentation related to crew training; NSB's proposal to reduce inspection frequency was rejected; a lack of analysis regarding potential critical incidents; absence of a designated safety inspector for operational and maintenance activities; and the trains' weight surpassing the allowed axle load. Det Norske Veritas (DNV) highlighted vulnerabilities in the axles. NSB enlisted Deutsche Bahn experts for testing, but their limited availability caused a six-month delay in inspections.

On 28 October 1999, Transport Minister Dag Jostein Fjærvoll convened a meeting with leaders from NSB, the inspectorate, and the National Rail Administration to address these issues. Despite identifying multiple safety shortcomings—such as missing deviation reports, no automatic speed control when automatic train stop systems were disabled, inadequate crew safety training, lack of evacuation assessments, and improper labeling of safety equipment—the inspectorate approved the trains for operation. Most of these deficiencies were scheduled for rectification within two weeks. Quale from the inspectorate commented that these deviations were unprecedented but did not pose immediate critical risks.

The initial train arrived on 22 October and commenced service on the Sørland Line starting 1 November. This reduced scheduled journey times by 40 minutes, bringing travel duration down to 3 hours and 40 minutes. In December, pantograph malfunctions during cold weather caused power outages and significant delays. NSB attributed these problems partly to the preceding mild winter, which limited testing under extreme conditions. After approximately two and a half months in operation, half of the trains experienced delays of at least five minutes, with one in ten delayed by over twenty minutes. Reports emerged of motion sickness affecting passengers and staff alike, especially on routes between Kristiansand and Bø. NSB noted that similar issues had occurred on older trains and suggested these reports might have been exaggerated.

On 16 December 1999, NSB confirmed an option to acquire six additional Class 73 units for NOK 680 million intended for deployment on the Østfold Line. The Class 73 trains began operating on the Dovre Line (Oslo–Trondheim) and Sørland Line (Kristiansand–Stavanger) from 7 January 2000. This reduced travel time from Trondheim to Oslo to 5 hours and 46 minutes. An independent survey indicated greater customer satisfaction with Signatur trains compared to airlines Braathens and Scandinavian Airlines, although overall reputation remained lower. By May, ridership on the Sørland Line decreased by 10%, attributed to reduced weekend capacity since Class 73 trains provided fewer seats than previous services. Additional services were introduced on the Dovre Line from June 11, while deployment on the Bergen Line was postponed pending necessary infrastructure upgrades.

Axle issues

On 17 June 2000, a Class 73 train derailed at Nelaug Station along the Sørland Line due to a fatigue fracture in the leading axle. Although the train was moving at a low speed and no injuries were reported, this event led to an immediate suspension and thorough inspection of all Class 71 and 73 trains. NSB admitted that the inspections conducted were insufficient. Following ultrasonic testing on Class 71 trains, these units were soon allowed back into service. A report by DNV identified the cracks as resulting from rust formed beneath the corrosion-resistant coating caused by trapped water.

Concerns about approval procedures were raised on 23 June by regulatory authorities, highlighting that testing had been performed under less strenuous conditions on the Dovre Line with lighter Class 71 trains, which did not reflect the increased stress from curves on the Sørland Line affecting Class 73 axles. NSB contested these claims, referencing their own test results and pledging extensive re-evaluation before permitting trains to operate again.

NSB intended to negotiate a price reduction with Adtranz due to higher maintenance expenses—inspections were required every instead of every , increasing costs by NOK 20 million annually. The contract stipulated that Adtranz was financially accountable for excessive upkeep demands. By late June, additional cracks were detected in two more train sets. Comparable problems had been reported in Swedish X2 trains using axles from the same manufacturer, linked to steel impurities and axle dimension issues.

Earlier in April, NSB had recognized incomplete axle inspections as a procedural flaw but delayed action since no prior warning signs indicated risk. This oversight resulted in CEO Ueland’s dismissal on 29 June, followed by his deputy’s resignation. Adtranz accepted full responsibility and assured coverage of costs, advising inspections every —a frequency NSB found impractical operationally. A compromise inspection interval of three weeks was ultimately established.

Operations resumed on 13 July at standard speeds with weekly inspections implemented. NSB eliminated surcharges on Signatur services and contemplated canceling orders for four undelivered trains due to persistent braking and air conditioning faults. In August, tilting systems were deactivated after bearing defects surfaced, while brake system failures triggered unintended automatic stops.

The fundamental cause was identified as rubber washers used in early units instead of standard plastic covers; these retained moisture, which led to axle corrosion and subsequent cracking. Adtranz had relied solely on paint coatings for corrosion defense—a method criticized by DNV inspectors—and axles were undersized. DNV declared that operation was only safe under restricted conditions and mandated axle replacement. NSB imposed a two-week deadline on Adtranz to rectify the problems or face contract termination.

In September, it became known that NSB had approved inferior steel quality for Class 71 axles back in 1996 to meet weight and speed criteria; this specification was carried over to Class 73. Adtranz accepted liability for the axle defects and pledged NOK 70 million for replacements. By October, they also agreed to replace all wheels on Classes 71 and 73 amid monthly brake system expenses of NOK 1.5 million borne by NSB.

Disagreements over compensation amounts continued, with a NOK 100 million difference between parties. In July 2001, NSB switched inspection providers from DNV to CorrOcean, reducing inspection costs by half. Bombardier Transportation, having acquired Adtranz, consented to replace bogie frames on Classes 71, 73, and 93 as part of settlement agreements with NSB.

Bergen and Østfold

Trial runs for the initial B-series trains took place on 7 March 2001. By May of that year, NSB admitted that the tilting trains could not reach the previously promised speeds, restricting their operation to standard train velocities for at least twelve months. On 17 September 2001, these trains officially began service on the Bergen Line connecting Oslo and Bergen. Throughout the subsequent winter, operations were hindered by snowdrift problems, necessitating reduced speeds due to frost heave affecting sections of the route. Performance evaluations indicated that Class 73 outperformed the older El 16 locomotives but did not match the capabilities of the El 18. In January 2002, NSB modified A-series trains to expand baggage capacity, responding to passenger needs for ski equipment transport.

Initially, the B-series operated on the Sørland Line between Kristiansand and Stavanger under the Agenda brand. Their introduction on the Østfold Line was postponed because of concerns related to axles and wheels, as well as heavy commuter traffic on that route. NSB also highlighted differences between A- and B-series trains: B-series lacked staffed dining cars, limiting their suitability for intercity travel, whereas A-series offered insufficient seating capacity for regional services. The B-series commenced operations on the Østfold Line on 6 January 2003, promising enhanced comfort and fewer delays caused by icing, with a top speed of . In June 2003, NSB phased out the Agenda and Signatur brands and revised timetables to better align with conventional trains, resulting in slightly longer travel times than those recorded in 1982. Starting from 15 December, certain Østfold Line services were extended to Gothenburg, Sweden.

On 21 February 2007, a Class 73 train derailed after colliding with an avalanche on the Bergen Line, raising questions about its reliability in harsh winter conditions. A prior report by DNV had cautioned that Class 73 units might slide over snow similarly to sleds. Experts argued that locomotive-hauled trains were more appropriate for such environments due to their heavier front ends providing better snow-clearing ability. In response, the National Rail Administration began deploying snowplow units ahead of Class 73 services during snowfall events. Although NSB considered reverting to conventional trains, they continued operating Class 73 pending further evaluation.

NSB maintained confidence in Class 73’s performance and kept them running on the Bergen Line. Alternatives involved using El 18 locomotives with B5 carriages; however, these were already allocated to regional peak-hour services and lacked suitable intercity features. In October 2007, NSB announced intentions to withdraw Class 73 from Bergen Line operations due to operational inflexibility—multiple units needed doubling up for capacity increases rather than simply adding individual carriages as with locomotive-hauled trains. Delays in carriage deliveries postponed upgrades beyond 2010.

On 16 June 2011, a fire erupted inside a snow tunnel near Hallingskeid Station, necessitating emergency evacuation of a two-unit Class 73 train carrying 257 passengers. The train lost power close to damaged overhead wires and stopped near the blaze; fortunately, no injuries were reported. The train was ultimately destroyed by fire. Following this event, plans were made to phase out Class 73 units from Bergen Line service beginning in autumn 2012.

Mid-life overhaul

In May 2014, Dutch railway refurbishment specialist NedTrain was awarded the contract to upgrade the entire fleet. The first trainset arrived for assessment and scheduling of refurbishment work in May 2014, with subsequent units planned for overhaul starting in spring 2015. All trains were transported by rail through Sweden, Denmark, and Germany en route to NedTrain’s primary facility located in Haarlem.

Go-Ahead Norge

Starting in December 2019, seven train sets commenced service on the Oslo–Stavanger line under the management of Go-Ahead Norge, following the company's successful bid for the contract.

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