They would also be able to haul full loads, at 110 kilometres per hour (68 mph), on the 1-in-37 (2.7%[2]) gradients of the Gotthard and Lötschberg routes in Switzerland.

Single phase AC motors were a new and untried technology for this application; earlier railway systems had recognised their advantages, but they had limited the line frequency to  16+2⁄3 Hz.

Powerful motors could not yet manage the problems of either core losses or the reactive behaviour of their windings causing flashovers of the brushgear.

Counted from driver's cab 1 end With hindsight, the locomotives never operated scheduled services East of France and never required their fourth voltage ability.

The weight of the quad voltage equipment required additional carrying axles, more than the typical French Bo′Bo′ layout of the time.

These Alsthom-bogied B′B′ designs, such as the BB 8500 class, had not yet acquired their nickname of «Danseuses», owing to their poor stability at speed.

[7] The monomotor bogie had the ability to change the gear ratio between the motor and the wheels, allowing a mixed-traffic locomotive to operate for either high-speed passenger or freight services.

Later classes with this design style had a longer cellular bonnet ahead of the driver, which could act as a crumple zone in an accident.

[8] This carried the same Inox livery as the locomotives, of ribbed stainless steel with a horizontal red stripe above the windows, labelled 'Trans Europe Express' in gold.

Their design was based on the 1952 lightweight, luxury Vehicle DEV Inox [fr], made from ribbed stainless according to the methods of the US Budd Company.

In 1969 a further series of coaches based on the PBA design, the Voitures Mistral 1969 [fr], were constructed for services on PLM routes to southeast France.

[iv] The last coach had only utility accommodation: 15 seats for train and customs staff, a baggage compartment and the air-conditioning generator set.

In 1969, shortly after its delivery, Nº 40106 was destroyed by a collision with a truck on a level crossing near Lembeek in Belgium.

The class had provided a good service but they were also judged to be insufficiently reliable and very expensive to maintain.

TEE was replaced by EuroCity in the early 1990s and then the high-speed line of LGV Nord, operated by Thalys.

Three locomotives have been preserved: All members of the class received names, chiefly of French communes, towns and cities.