The Howard Street Tunnel fire (also known as the Baltimore Freight Rail Crash) was a 60-car CSX Transportation freight train derailment that occurred in the Howard Street Tunnel, a freight through-route tunnel under Howard Street in Baltimore, Maryland, on July 18, 2001. The derailment sparked a chemical fire that raged for five or six days and virtually shut down the downtown area. In the evening of the first day, a water main ruptured causing significant flooding in the streets above. The accident disrupted Northeast Corridor rail service. It also slowed Internet service in the US for several hours due to the destruction of a cable passing through the tunnel. The derailment and fire The train consisted of 60 cars. Cars 46 through 56 derailed in the Howard Street Tunnel at 3:08 PM, and became disconnected from the first 45 cars. The train experienced an automatic emergency brake application resulting from the separation of the train, but the crew didn't realise that a derailment had taken place. Around 3:26 they moved the locomotives out of the tunnel. Around 4 PM smoke was seen coming from a sewer near the intersection of Howard and Lombard Streets, and the fire department was notified. Later, smoke emerged from the ends of the tunnel and from several manholes. Eventually it was found that one of the derailed tank cars, carrying tripropylene, had ruptured and the escaping flammable liquid had caught fire. This fire also ignited paper and wood products in other cars. Another tank car ruptured releasing of hydrochloric acid. Around 6:15 a 40-inch cast iron water main above the tunnel burst due to deformation, eventually releasing about of water. The fire burned for about 5 days. A National Transportation Safety Board report took three years to be prepared. The investigation was not able to find the cause of the accident. A numerical simulation by the National Institute of Standards and Technology found that the peak calculated temperatures within the tunnel were approximately within the flaming regions, and on average approximately when averaged over a length of the tunnel equal to three to four rail car lengths. Due to the insulation of the tunnel's thick brick walls, the temperature was relatively uniform across all the cars, approaching temperatures normally found in an oven or furnace: The peak wall surface temperature reached about where the flames were directly impinging, and on average over the length of