Jennifer Homendy, chairwoman of the National Transportation Safety Board, suggested that the deadly crash involving an Amtrak train and a dump truck could have been avoided. Four people were killed, and 150 were injured when the train slammed into a dump truck that was crossing the track in Mendon, Missouri.

Homendy said that the crash occurred in a "passive crossing" that did not have any lights or mechanical arms to block the tracks when a train is coming. Instead, the crossing only had a stop sign. She said that the agency has recommended that local officials upgrade all their passive crossings to active ones with gates, lights, and bells, to alert drivers that a train is approaching.

Homendy said it would cost about $400,000 to upgrade the crossing where the crash occurred.

"Anytime our recommendations aren't heeded, of course, I'm upset because we see tragedy after tragedy after tragedy and numerous fatalities and injuries," Homendy said during a news briefing. "It's very frustrating for our investigators, very frustrating when they are on scene, and they know what would have prevented this."

Homendy said that about half of Missouri's roughly 7,000 railroad crossings are passive and noted the local officials are working on upgrading them. She added that there are approximately 130,00 passive railroad crossings throughout the country.

Homendy said that investigators do not believe the crash was the result of mechanical failure, noting that the train was traveling at 87 mph, just below the speed limit of 90 mph at the time of the crash. She said that investigators are looking at the design of the crossing to see if drivers have a clear view of the tracks.

"I do not have concerns about mechanical failure about the train, any mechanical issues with the train. We do not have concerns about the track," Homendy said. "Our concerns are very focused on this grade crossing, the approach to the grade crossing, and survivability after an accident."