What happened to the Mont Blanc Tunnel?

On 24 March 1999 a large multi-vehicle fire broke out inside the Mont Blanc tunnel. The fire claimed the lives of 39 people, closed the tunnel for three years and resulted in fines for companies involved and suspended jail terms for manslaughter.

Until this incident vehicle fires had been extinguished by tunnel staff.

How did the Mont Blanc Tunnel fire start?

The source of the fire is disputed, but one theory is that a  cigarette may have entered the filter system on board a Belgian truck with a refrigerated trailer.

At around 10:50am a Belgian truck entered the 11.6km tunnel. Within five minutes smoke from the truck was seen and the driver alerted by oncoming commuters.

Alarms in the tunnel sensed the smoke and switched on cameras in the vicinity on the French side of the tunnel. A false alarm the previous day had disabled the facilities on the Italian side).

The cameras observed the scene as the driver stopped the truck and stepped out before it exploded into flames. The monitor operator remained unaware up to this point. The driver and other commuters ran for their lives while others kept vehicle windows up and waited to be rescued.

The truck had travelled approximately 6km into the tunnel - black smoke rapidly moved in both directions which decreased visibility. 10 minutes into the fire the tunnel’s lighting and emergency lighting systems failed.

Increasing hot toxic gases raised the temperature to around 1,500 - 1,800°C - so intense that the chassis of a motorbike was found melted into the tarmac.

14 minutes into the fire the first fire engine left its base having been contacted by the monitor operator. The fire was now well-established - it had engulfed around 30 vehicles up to a distance of 6km away from where it started.

What can the industry learn from the Mont Blanc tunnel fire?

The inquiry discovered that in 34 years of operation the facility had only practised one fire drill. This led to reassessment of safety protocols. The tunnel now has:

• Fire-resistant sheeting fitted to its walls
• More traffic lights and flashing warning signs
• 37 concrete lined shelters located at 300 metre intervals
• 116 smoke extraction systems (one located every 100 metres) and 76 fresh air vents
• Heat detection at both ends of the tunnel to redirect vehicles before they enter the tunnel if necessary
• 120 video cameras to monitor traffic 24hrs
• A central command post managed 24hrs