Shuttle blaze was good test for engineers

THE CHANNEL Tunnel fire taught engineers a basic lesson: "When lorries go through tunnels, whether by road or rail, they catch fire," said Antony Oliver, the deputy editor of New Civil Engineer magazine. "Not often, but eventually."

The fire in the Mont Blanc tunnel has exposed the fact that there are no clear international standards for tunnel building. In Britain, responsibility for overseeing tunnel design depends on what it will be used for: road tunnels are handled by the Highways Agency, railways by Her Majesty's Railway Inspectorate (part of the Health and Safety Executive), and pedestrian tunnels (such as that beneath the Thames linking Greenwich and the Isle of Dogs) ... nobody is quite sure.

But civil engineers do now expect that there will be fires in any tunnel they design, and plan accordingly. With temperatures able to reach 1,000C in a serious fire, the heat resistance and dissipation capacity of the material is a key to people's survival. The Channel Tunnel blaze in December 1996, when a lorry on a Le Shuttle service caught fire and caused severe damage to the tunnel interior, was a key test of the lining's ability to withstand intense heat. It passed.

There are no guidelines or design rules about, say, the ratio of a tunnel's cross- section to its length that might predict how quickly smoke overwhelmed an area. "We have design standards, but they always have to take account of the location of the tunnel," said a Highways Agency spokeswoman. "Some of the tunnels under our jurisdiction were built before the agency was set up. We can't change them."

The aim is to try to prevent fire in the first place but this is an impossibility. "People said it couldn't happen in the Channel; it did. And now it has happened again," said Mr Oliver.

The solution does not lie in banning lorries with "dangerous" substances: the one that caught fire this week carried margarine, butter and flour.

The Mont Blanc tunnel is at present the longest in the world - though a much longer one, the 25km Laerdal tunnel, will open in Norway next year or the year after. Sooner or later, the fire design will be tested - how will it fare?