If a fire were to occur on a HGV in a closed wagon it is quite possible that it would become oxygen-starved and self-extinguish. In any case the fire development would be expected to be relatively slow and the train would likely be out of the tunnel before any significant danger had been created. Retaining the semi-open wagons means that a complex inter-connected system will need to come into play and operate reliably. This would involve detection and communication systems and, crucially, the Supplementary Ventilations System (SVS) which would create a longitudinal ventilation (a wind) along the tunnel to push smoke away from the amenity carriage, near the front of the train, in which the lorry drivers would be travelling.
In the fire of November 1996, the SVS did not come into operation until a long time after it should have done. Also, the conflagration involved the last six lorries in the train, nearly half a mile from the amenity carriage. If the fire had involved the first six lorries, then it is extremely likely that deaths would have resulted.
If a fire were to involve the first six lorries, the SVS would need to produce a strong ventilation flow. Such a wind would probably be very upsetting and quite possibly disorienting for anyone attempting to escape through it. It is even possible that the force would knock some people over.
Procedural changes are required, as the Safety Authority report indicates. However, they should be made in addition to the introduction of closed wagons, not instead. Not to require closed wagons is rather like replacing the Forth Rail Bridge by a computer-controlled machine with gigantic mechanical legs which would carry each train across the Forth on a platform. It may work, but there is much more scope for something to go wrong.
It appears that the Safety Authority has given a greater weight to commercial considerations than to public safety. The apparent reason for having semi- open wagons is that fully closed wagons would mean that 44-ton HGVs could not be carried because the extra weight would be too great for the undercarriage. This would eat into Eurotunnel's projected profits. This problem could, however, be overcome either by carrying the smaller 37-ton lorries only or by developing a stronger undercarriage.
As a society, we tend to wait until lives are lost before we really try to bring about effective change. Witness, for example, Piper Alpha or the fire hazard of polyurethane foam in furniture.
Dr ALAN N BEARD
Department of Civil and Offshore Engineering