There are usually 28 wagons to each freight shuttle.
The original intention was to design the individual wagons so that they were fully enclosed just as the passenger shuttles are. Drivers would then be able to remain in their cabs for the 35-minute journey and drive off immediately at the other end.
The Anglo-French InterGovernmental Safety Authority objected, however, on safety grounds. It insisted that drivers travel instead in a separate amenity carriage and asked Eurotunnel to modify its design.
Eurotunnel soon discovered that there were pressing reasons other than safety for not going ahead with a closed carriage design - weight, cost and operational efficiency.
The company discovered that, together with the weight of the lorries themselves, a closed wagon design would place more strain on the shuttles than they could bear.
It also discovered that the cost would be excessive. When construction of the tunnel began in autumn 1987, the cost of the entire fleet of freight and passenger shuttles was put at pounds 252m. Within three years that figure had ballooned to pounds 603m.
By that time Eurotunnel had abandoned the original design and opted for the semi-open design based on the Alpine rail tunnels where passengers, cars and freight have been carried since the 1960s without incident.
The change in tack prompted immediate concern. The Kent fire brigade warned of the dangers of fire being able to spread rapidly from one freight wagon to another. The Commons Select Committee on Home Affairs voiced concern.
Eurotunnel pressed ahead, however, with its design. Fire and safety tests were carried out at two locations - in Italy where the manufacturer of the wagons, Fiat Breda, has its own test-bed, and in Hammerfest in northern Norway where one complete freight shuttle was fire-tested in a specially built tunnel.
Finally in October, 1993, the InterGovernmental Safety Authority announced that it had no objections to the semi-open shuttle design.
By that time, however, Eurotunnel had already placed advance orders for the fleet, a move that angered MPs on the home affairs committee.
Eurotunnel is now buying a further 16 freight shuttle wagons and two entire freight shuttle trains. This time the order has been placed with a Belgian manufacturer, Arbel, because, Eurotunnel says, its bid was a third lower than the price charged by Fiat Breda. The eventual price will depend, however, on whether Eurotunnel is forced to re-design its entire fleet of freight shuttles.Reuse content