# Non-standard rail traction
Non-standard rail traction is railway propulsion that falls outside the mainstream classification of rail vehicles as steam, diesel, or electric. An example is the [Aérotrain](https://www.edgepedia.org/aerotrain), the French hovertrain created by engineer Jean Bertin, which rode on a cushion of pressurized air over an inverted-T concrete track without ever touching the surface[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
| Key fact | Figure |
|---|---|
| Aérotrain hovertrain principle | Rode on pressurized air over an inverted-T concrete track with no physical contact[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/) |
| I-80 top speed on the Orléans test track | 250 km/h, attained 13 September 1969 on the 18 km guideway[2](http://aernav.free.fr/Aerotrain/Anglais/Aerotrain_Story.html) |
| US Tracked Air Cushion Vehicle research budget | US$90 million, under President Lyndon Johnson's Department of Transportation[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/) |
| Shanghai Transrapid maglev | ~19 miles in 8 minutes; capable of 268 mph, cruising capped at ~186 mph[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/) |
| Saint-Germain atmospheric railway cost | 6,137,633 francs total, exceeding state and city allocations by 4,137,633 francs[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques) |
| Saint-Germain track premium vs locomotive line | Double where tube diameter was 0.38 m; quadruple where it was 0.63 m[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques) |
## Why standard taxonomies fail
The steam–diesel–electric scheme classifies traction by on-board energy source and conversion, but some rail-bound vehicles fit neither mold. The Aérotrain is one such example, the French hovertrain created by engineer Jean Bertin: it rode atop a cushion of pressurized air pumped downward between the vehicle and a concrete track shaped like an inverted T, lifting it so it never made physical contact with the surface[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
Such a vehicle cannot be called a locomotive in any conventional sense. It has no wheels to drive, no rail contact, and its propulsion is bound to a purpose-built guideway. Non-standard in this article therefore means traction whose relationship to the guideway, or whose power transmission, departs from the wheel-on-rail, energy-source mold, not merely traction that is rare or experimental.
## Cross-cutting themes
Three axes organize the outliers better than the standard taxonomy does.
**Energy source** separates, for example, atmospheric systems, where machinery external to the vehicle moves it through a pipe, from vehicles carrying their own fuel. The Aérotrain was air-propelled in the tracked air-cushion sense: lift came from pressurized air, and the US research program it inspired was built around these so-called Tracked Air Cushion Vehicles[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
**Power transmission** distinguishes vehicles that convert energy on board from those pushed or pulled by external infrastructure. Atmospheric railways are the historical case.
**The guideway relationship** is the deepest axis, because it separates every conventional vehicle, which must match existing track, from vehicles demanding new infrastructure of their own. The Aérotrain's inverted-T guideway and the [Shanghai Transrapid](https://www.edgepedia.org/shanghai-maglev-train) maglev, capable of 268 mph though capped at around 186 mph in service over the roughly 19 miles between Pudong International Airport and Longyang Road station, both required dedicated infrastructure[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/). Maglev trains trace their roots to technology developed at [Brookhaven National Laboratory](https://www.edgepedia.org/brookhaven-national-laboratory), and operating systems include services in China, Japan, and South Korea, so the guideway-bound family is not purely historical[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/) • [4](https://stage.energy.gov/articles/how-maglev-works).
## Historical near-standard types
Some non-standard traction once competed to become standard and lost. Atmospheric railways of the 19th century are a well documented case, because contemporary engineers argued about them in numbers.
The Saint-Germain atmospheric railway shows the economics. Its track cost double a locomotive-worked line on the section where the propulsion tube was 0.38 m in diameter, and quadruple where the tube was 0.63 m; the whole line was valued at 6,137,633 francs, exceeding the state and city allocations by 4,137,633 francs[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques). The contemporary French engineering literature concluded that, in the state of things at the time, the atmospheric system was not financially applicable[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques).
Contemporary estimates of atmospheric traction's viability disagreed sharply, and the disagreement was never resolved. Engineer Mallet, comparing locomotive-worked lines with lines using pneumatic propulsion under the same conditions, concluded that the pneumatic lines would show an establishment-cost saving of 70,000 francs per kilometer[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques). Engineer Crelle counter-estimated that building the Berlin–Potsdam railway as an atmospheric system would cost 53,000 francs per kilometer more in construction, plus 20,000 francs more per year in operation and maintenance[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques). Both figures are presented here as contemporaries stated them; the sources do not reconcile them.
The hovertrains of the 1960s and 1970s repeated the pattern at larger scale. Bertin's Aérotrain I-80 was presented at Le Bourget on July 7, 1969, moved days later to the Orléans test base, and on its 18 km guideway attained 200 km/h on September 12 and 250 km/h on September 13, 1969, the maximum speed recorded there[2](http://aernav.free.fr/Aerotrain/Anglais/Aerotrain_Story.html). The United States, inspired by Bertin's design, formed the Office of High-Speed Ground Transportation and funneled $90 million into Tracked Air Cushion Vehicle research, producing prototypes including Rohr Industries' Aerotrain and Grumman's Tracked Levitated Research Vehicle[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
What killed the hovertrains was infrastructure compatibility. The upfront cost of building entirely new concrete or electromagnetic guideways made their economics nearly impossible to justify, while wheel-on-rail trains such as France's TGV remained compatible with over a century of existing infrastructure[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/). In France, a global recession and the oil crisis of the 1970s left the government, whose funding was essential, with little appetite for large, time-consuming infrastructure gambles, and the Aérotrain's single contracted route was never built[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
## By the numbers
The quantitative record for non-standard traction is sparse and mostly historical.
- Atmospheric railways: Saint-Germain total cost 6,137,633 francs, of which 4,137,633 francs over allocation, with track costing two to four times a locomotive line depending on tube diameter[3](https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques).
- Hovertrains: an 18 km French test guideway, top speed 250 km/h[2](http://aernav.free.fr/Aerotrain/Anglais/Aerotrain_Story.html); US$90 million of American research producing prototypes[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
- [Maglev](https://www.edgepedia.org/maglev), the surviving descendant: Shanghai's ~19 mile, 8 minute airport link at 268 mph capability and ~186 mph cruising[1](https://www.popsci.com/technology/first-hovertrain-aerotrain/).
## References
1. The world's first 'hovertrain' could reach speeds of 270 mph in the 1960s, Popular Science. https://www.popsci.com/technology/first-hovertrain-aerotrain/
2. Aérotrain et Naviplanes, The Aerotrain Story. http://aernav.free.fr/Aerotrain/Anglais/Aerotrain_Story.html
3. Les Chemins de fer atmosphériques, 19th-century French engineering periodical (Wikisource transcription). https://fr.wikisource.org/wiki/Les_Chemins_de_fer_atmosph%C3%A9riques
4. How Maglev Works, https://stage.energy.gov/articles/how-maglev-works
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*Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Rail transport › Rail vehicles and rolling stock › Classification, components, and unusual traction › Unusual and non-standard rail traction › Non-standard rail traction overview*
*Initially written Sep 17, 2026 · Edited: Oct 11, 2026; Oct 15, 2026; Oct 25, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license