On March 24, 1999, a fire broke out in the middle of the 7-mile-long Mont Blanc tunnel that eventually claimed the lives of 39 people. The Mont Blanc tunnel contained safety bunkers, but they weren’t rated for the fire that occurred, which burned for 50 hours and reached 1,800 degrees Fahrenheit. The disaster led to changes in tunnel design, emergency protocols, and a lawsuit that eventually indicted 13 people. On the morning of March 24, 1999, a Belgian truck driver named Gilbert Degrave sat behind the wheel of a Volvo FH12 tractor-trailer filled with margarine and flour. At around 11 a.m., while Degrave drove through the 7.2-mile-long Mont Blanc tunnel—a nearly 35-year-old architectural wonder that snakes beneath the Alps to link the French and Italian highway systems—his payload mysteriously caught fire. To this day, no one is exactly sure what caused the initial spark, but the resulting aftermath is brutally certain. The blaze melted the margarine, forming a highly flammable vapor that superheated the tunnel up to 1,800 degrees Fahrenheit, and the flames became too hot for other vehicles to simply drive past. The combination of thick smoke and scorching temperatures eventually killed 39 people, including motorists, rescue crews, and a 36-year-old security guard who lost his life trying to save others. The fire eventually spread to an estimated 20 tractor-trailers and dozens of other vehicles. “Initially, there was a lot of conjecture, and uneasiness, about how a fire of that size could become so deadly and produce so much damage,” William Connell, a tunnel systems engineer, told The New York Times on the 20th anniversary of the accident. “When the full report on the Mont Blanc fire finally came out, it was evident that additional measures of fire protection and emergency response planning would have reduced the significance of the fire.” The event shocked Europe, instigated debates around the tunnel’s safety and the increasing volume of traffic on European highways, and helped motivate the eventual formation of the French Land Transport Accident Investigation Bureau. Despite more than a dozen small fires that had taken place in the tunnel over its then 35-year-long history, no fire deaths had occurred in the tunnel until that fateful day in the spring of 1999. The creation of the Mont Blanc tunnel was a herculean task. Drilling of the single-bore, two lane tunnel began in 1959, and was eventually completed three years later. When the tunnel opened for business in 1965, it was the largest longest road tunnel in the world (an accolade that now belongs to the 15.23-mile-long Lærdal Tunnel in Norway). The tunnel contained a ventilation system (which remained largely unchanged until the 1999 fire), as well as emergency bunkers every one-fifth of a mile rated to withstand up to a four-hour-long fire. According to The New York Times, the Mont Blanc tunnel fire burned for 50 hours—an unfortunate scenario that eventually claimed the lives of the 36-year-old security guard, Pierlucio Tinazzi, and the stranded trucker he tried to save. Many motorists couldn’t even reach these bunkers, as toxic fumes from the smoke and prevailing darkness eventually incapacitated them on the road itself. While additional fire protection measures would have save lives, the confusion of the joint Italian-French response was also partially to blame for the devastation of the fire. At one point, for instance, security officials on the Italian side of the tunnel pumped in fresh air that only fanned the flames toward the French side, imperiling trapped motorists even further. The Mont Blanc tunnel remained closed for three years following the deadly accident to repair sections of the tunnel’s ceiling that had collapsed, introduce much-needed safety upgrades (including fire-resistant materials), and improve safety protocols. In 2005, a lawsuit against several individuals and companies, including the truck driver and Volvo, found 13 people guilty in the unfortunate tragedy. To this day, an annual motorcycle rally at the tunnel is held in honor of Tinazzi and all the other motorists who lost their lives.