WASHINGTON, D.C. — An inattentive driver and faulty brakes were the probable cause of a fatal accident in which a heavy commercial truck struck a passenger train in the Nevada desert last year, the National Transportation Safety Board (NTSB) said on Tuesday.

On June 24, 2011, a 2008 Peterbilt truck-tractor pulling two empty trailers on northbound U.S. 95 struck the left side of an Amtrak train that was passing through a grade crossing. The collision, which destroyed the truck-tractor and several passenger railcars, also ignited a fire that engulfed two railcars and part of a third.

The accident killed the truck driver, the train conductor and four train passengers. Fifteen train passengers and one crewmember were injured.

NTSB officials said that when the grade crossing signals activated, the truck, traveling at least 58 mph, was still more than 2,300 feet from the tracks. However, investigators found no evidence that the truck driver began braking until the front of the truck was less than 300 feet from the crossing.

“Although we’ll never know the exact cause of the truck driver’s inattention, we do know that if John Davis Trucking had provided its driver with a safe and properly maintained vehicle, this accident could have been avoided,” NTSB Chairman Deborah Hersman said.

Reconstruction of the accident using a recording from a forward-facing video camera mounted on the front of the train as well as physical evidence helped investigators to determine that the truck struck the crew car of the train at 26 to 30 mph.

The investigation revealed that nine of the 16 brakes on the truck were either out of adjustment or inoperative. In addition, the anti-lock brake systems of both trailers were not functional. Wires to missing sensors were cut and zip-tied, and wires to malfunction indicator lights had been disconnected, which the NTSB said raised "serious questions" about the maintenance practices of the trucking company.

Several months after the collision, NTSB investigators returned to the accident site and conducted a series of tests with an exemplar truck in which the braking system was in proper working order. Test results showed that if the accident truck had been able to decelerate as well as the exemplar vehicle, the accident would have been avoided, with the accident truck coming to a stop 15 to 67 feet short of the rail tracks.

As a result of the investigation, the NTSB made a total of 20 safety recommendations to various entities, including John Davis Trucking, the Federal Motor Carrier Safety Administration, the National Highway Traffic Safety Administration (NHTSA), the Federal Railroad Administration, the American Trucking Association, the American Bus Association and the United Motorcoach Association.

To NHTSA, the safety board recommended requiring that all newly manufactured air-braked commercial vehicles be equipped with onboard brake stroke monitoring systems.

A synopsis of the NTSB's report, including the probable cause, findings and a complete list of the safety recommendations, is available here. An animation of the accident reconstruction is available here.

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