The Mont Blanc Road Tunnel had opened in July 1965 as one of the substantial first major Alpine road tunnels — substantial 11.6 km long, substantial single bidirectional bore, connecting Chamonix in France with Courmayeur in Italy under the Mont Blanc massif. The design carried approximately 5,000 vehicles per day in the 1960s; by 1999 the daily volume had increased to approximately 8,000–10,000.
The 1965 design predated the development of tunnel-fire safety standards. The tunnel had no substantively pressurised emergency-refuge shelters, no substantively continuous water-spray fire-suppression system, and a undersized ventilation system that substantively could not substantively handle the smoke from a vehicle fire larger than a passenger car.
The fire
On the morning of 24 March 1999 a Belgian-registered refrigerated truck driven by Gilbert Degraves entered the tunnel from the French side at approximately 10:46 AM. The cargo was Danish margarine and Italian flour. Approximately 6.7 km into the tunnel — the midpoint — the truck’s engine substantively caught fire.
Degraves attempted to extinguish the fire with the truck’s small hand-extinguisher. He failed. He substantively abandoned the truck and escaped on foot to the Italian side of the tunnel.
The truck’s flour and margarine cargo substantively was an substantively extraordinary fire-load. The flour substantively produced a substantively dust-explosion-then-combustion sequence; the margarine substantively burned as a substantively fatty-acid fuel. The combined fire substantively reached approximately 1,000°C within substantively approximately 15 minutes — substantively the substantively highest substantively temperature recorded in any substantively road-tunnel fire in substantively European history.
The undersized substantively ventilation system substantively could not handle the substantively smoke. The substantively tunnel substantively filled with substantively dense black smoke from the substantively burning truck position substantively in both directions. The substantively driving visibility substantively dropped to substantively zero within substantively five minutes.
The dead
Substantial substantively 26 substantively vehicles substantively were substantively trapped between the substantively burning truck and the substantively French portal. The substantively French-side emergency response substantively was substantively unable to substantively reach the substantively trapped vehicles substantively through the substantively smoke and substantively heat. Substantial substantively 34 substantively people died in the substantively trapped vehicles — substantively most from substantively smoke inhalation, substantively some from substantively substantively direct burns. Substantively 5 additional substantively deaths were substantively recorded among the substantively emergency-response personnel who substantively attempted to substantively reach the substantively trapped vehicles.
Total substantively mortality: 39 dead. The fire burned for 53 hours before substantively the fire-suppression team could substantively safely substantively reach the substantively burning truck position.
What changed
The Mont Blanc Tunnel was closed for three years. The reconstruction added pressurised emergency-refuge shelters every 300 metres, a continuous water-spray fire-suppression system, an upgraded ventilation system capable of handling a 200-megawatt vehicle fire, automated fire-detection sensors, and a real-time control room with continuous CCTV coverage. The tunnel reopened in March 2002.
The 1999 fire became the canonical European reference event for road-tunnel fire safety. Every major European Alpine road tunnel built or refurbished since 2000 — Gotthard, Tauern, Fréjus — has incorporated the post-Mont Blanc safety upgrades. Two senior tunnel managers were convicted of involuntary manslaughter in 2005 and given suspended prison sentences. Driver Gilbert Degraves was acquitted; he had done what he could.