Understanding the deadliest truck crashes

The remote-controlled tractor-trailer accelerates along the test course, gets up to speed and cuts slightly left then quickly hard right, causing the inevitable flip of the truck onto the driver's side. It's a test demonstrating how a side protection system works, and different camera views show the forces acting on the driver when a heavy truck bangs to its side on the ground.

That's the kind of crash responsible for about half of some 700 trucker fatalities across the country each year, according to Larry Gray, CEO of Indiana-based commercial truck safety systems provider IMMI.

"Typically, there's a tanker or box [trailer] at the back of the truck, and that load can shift," he explains. "It has a high center of gravity, so there's a centrifugal force. If that starts to go [around a turn or corner], it'll take the whole tractor and it'll turn it over."

A truck's trailer can "go" over in a move like a hard right or left, as in the test IMMI conducted at a World War II airstrip with its Center for Advanced Product Evaluation (CAPE). Rollovers typically also happen when a truck veers off the road and into softer, uneven or banked ground, Gray notes.

As that high center of gravity in the trailer approaches the point of no return, the trailer loses balance and tips over ahead of the tractor, adding an accelerative force as it slams to the ground and whips the cab along with it.

Forces on the driver

If that happens, the driver of course comes along for the ride. Seats in a heavy truck are like shock absorbers on their own suspension, moving up and down to provide a more comfortable ride, says Tom Anthony, president of IMMI. In a rollover, the centrifugal force will pull the "shock absorber" seat upward — and the driver and passenger, if any, toward the ceiling.

Gray also describes the process. As the truck rolls over, "you go up to a high point in the vehicle [sitting on a suspension seat] and you smack your head and neck on a hard point of the vehicle, causing high injuries to the neck and high injuries to the head."

Those are the injuries that kill about half the truck drivers who die in crashes, Gray and Anthony explain, and IMMI's RollTek side roll protection airbag system aims to make them a thing of the past.

As its sensors detect a rollover accident in the truck is imminent, the RollTek system does three things:

• Tightens down the seat belt to pull in the driver and/or passenger securely at the hips and shoulders

• Brings the seat down to its lowest position

• Deploys a side-curtain airbag

The system thereby holds driver/passenger more securely to reduce any movement during the crash, pulls them down into "the most survivable space" away from the truck's roof, and provides a cushion via the side airbag to keep them from slamming head/neck into the side of the truck.

"We can take what is potentially the most fatal of all accidents for heavy truck drivers and turn it into a walkaway — that's what we're striving for," Anthony says. The company notes its RollTek product is the only side-roll airbag protection system for heavy trucks in the U.S. market.

Watch video of the IMMI/CAPE rollover crash test:


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