Tracked Air Cushion Vehicle (TACV)

Before the Maglev (magnetic levitation) very fast train (VFT) system was developed—which we can observe today in commercial operation in Japan, China and South Korea—there was the Aérotrain prototype in France✳. Its story starts in the early 1960s when France was faced with a need to revitalise its declining railway sector. In 1963 aviation engineer Jean Bertin pitched his Aérotrain concept for a VFT mass transit system to France’s public transport czars. Over the next two years the government created a state company to study the Aérotrain while Bertin developed his 1:20 scale model train into the full-scale prototype.

Bertin’s invention was a Tracked Air Cushion Vehicle (TACV), a hovertrain riding on a cushion of air atop “a simple reinforced concrete track or guideway”∆. The Aérotrain design borrowed from the lifting technology of hovercraft vessels and from the arliner’s turbo fan. Both the ‘wheelless’ vehicle and the T-shaped track were radical designs at the time. Bertin’s intention was to come up with a simpler and cheaper alternative to the Maglev trains then in experimentation (‘France’s Aérotrain’, Ian Brown, Google Sighting, 10-Oct-2013, www.googlesighting.com).

Exporting the hovertrain
By 1966 Bertin & Cie had built its first Aérotrain test track (6.7km-long) at Essonne, south of Paris. Interest in Bertin’s hovertrain concept was international, Britain designed its own version, the RTV-31 Tracked Hovercraft, and constructed a test track in 1970, in the US, Rohr Industries contracted with Bertin’s company to do the same. Bertin developed several prototypes, the ultimate bring the Aérotrain 180 HV, a 25.6m-long hovertrain seating 80 passengers and attaining a world record speed for overland cushion vehicles (430.3 km per hour).

Technical issues
L’Aérotrain prototype presented Bertin with a series of design challenges — the system would require new elevated guideways for every implementation; the craft when passing other trains or entering tunnels experienced sudden changes in air pressure; the Aérotrain’s gas turbines operated with giant propellers which generated tremendous noise, necessitating a reduction in speed in urban areas (making it unattractive to some interested authorities) (‘Aerotrain’, Wikipedia, http://en.m.wikipedia.org).

Aérotrain, not the people’s train?
Although the technocrats in the state apparatus were favourably disposed to Bertin’s Aérotrain—especially DATAR (Delegation for Territory Planning and Regional Action)—its acceptance was not universal within France. Technical difficulties like the noise levels turned . many Parisians away from the vehicle. With such a “cutting-edge” special project, a perception grew that Aérotrain travel was for the elite commuter, not the average French worker, “(serving) only a rarefied strata of society”⟴ (Guigueno, Vincent. “Building a High-Speed Society: France and the Aérotrain, 1962-1974.” Technology and Culture, vol. 49, no. 1, 2008, pp. 21–40. JSTOR, www.jstor.org/stable/40061376. Accessed 20 June 2021).

Cost was increasingly a factor working against the Aérotrain, the system, requiring a dedicated track would be costly to implement. The 1973 oil crisis (also see End-note) and the imposition of new strictures on state spending didn’t help, leaving the Aérotrain Company in financial difficulties (Guigueno). Public authorities were increasingly reluctant to fund the Aérotrain project.

The modern versus the traditional
The bureaucracy and SNCF (French National Railway Company) had its own agenda, which deviated from the objectives of Aérotrain. Transport planning in France was committed to a policy of maintaining the efficacy of “traditional modes of urban transport”, heavily investing in Aérotrain ran counter to that. The influential SNCF saw it as a “competitive threat to the traditional railway” (Guigueno).

The lethal blow came in 1974. French president, Georges Pompidou, who had been a moderniser, died. His more conservative replacement, Valéry Giscard d’Estaing, coming down on the side of traditional technologies terminated the Aérotrain project just two months into office. The reasons for Giscard’s opposition to the project are not certain, Guigueno speculates that perhaps the president was reacting to Aérotrain’s unpopularity with the Paris suburbs and their representatives. The recently-approved Cergy—La Défense link for Aérotrain engendered scepticism from locals due to delays and cost overruns and was also canned by Giscard. Giscard whose previous ministerial job was controlling the nation’s pursestrings probably thought Aérotrain was too much of a financial risk at the time (‘Transport That Never Was Part 1: Aérotrain, a hovertrain in Paris’s western suburbs’, Fabric of France, 18-Feb-2020, www.fabricoffrance.com).

Replacing a revolutionary VFT with a conventional VFT
Aérotrain’s misfortune was TGV’s good fortune. The Giscard government switched from Aérotrain to TGV¶, a rival turbo train design inspired by Japan’s Shinkansen, as the preferred provider for France’s inter-city high-speed rail service. In 1981 TGV became the VFT carrier for the new Paris to Lyon link. Essential to TGV’s triumph over Aérotrain was SNCF’s strategy of “develop(ing) TGV as a supplement to, rather than a replacement for the traditional rail service” (Guigueno)❂. On the matter of infrastructure TGV was a full circuit in front of Aérotrain. The TGV was a better fit with its huge advantage over Aérotrain in compatibility with existing railways in France, and it could extend, beyond the high-speed network, over much greater distances (‘Transport That Never Was’).

Aérotrain’s eclipse was devastating for its inventor … Bertin, already stricken with cancer, died several months later, aged just 58. In 1977 the Aérotrain project was abandoned, bringing an end to the Gallic hovertrain dream.

End-note: The hike in the world oil price after 1973 posed an acute problem for the TGV prototype, being as it was powered by gas turbines. Sagely, the company switched its prototype to all-electric trains to overcome this, and stay cost-competitive with Aérotrain (‘Transport That Never Was’).

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✳ the Aérotrain’s levitation anticipated the magnetic floating effect of the later Maglev train (‘1963-1980 The Aérotrain’, Alex Q. Arbuckle, www.mashable.com)
∆ Bertin understood that by compressing and enclosing air under the vehicle, “it was possible to produce an air cushion over which the craft could glide with minimum resistance and power” (Kaushik Patowary, ‘Aerotrain: The High-speed Train That Almost Revolutionized Transport’, Amusing Planet, 19-May-2020, www.amusingplanet.com).
⟴ Aérotrain #02 prototype and the small cabin-sized Tridim for instance are personal-type vehicles, not mass transit vehicles
¶ TurboTrain à Grande Vitesse
❂ Britain followed a similar path to France, the experimental RTV-31 ended up in the dumpster, superseded by the more conventional APT-E tilting high-speed train

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L’Aérotrain Experiment: The Rise and Fall of a French Hovertrain