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The Tipping Point

By on March 1, 2008
David Kolman

I had the opportunity to attend one of several Rollover Prevention Summits put on by the National Tank Truck Carriers Conference. It was an enlightening experience.

In his remarks to the meeting, John Hill, administrator of the Federal Motor Carrier Safety Administration, noted that some 45 percent of injuries from single large truck accidents are due to rollovers and 52 percent of truck occupant fatalities involve a rollover.

As you might expect, cargo tank trucks are more likely than van trucks to roll over, often due to drivers not considering the continuous movement of liquid in the tank. Hill said 75 percent of all cargo tank truck rollover accidents are caused by driver error, while only 10 percent are due to excessive speed.

According to Triodyne, a mechanical engineering consulting firm that specializes in safety of engineering systems and mechanical devices, these are the basics of a truck rollover: When a truck travels in a curved path, it leans to the outside of the curve because of centrifugal force. That force increases with speed and with the curvature of the road.

The truck’s ability to resist rollover is determined by its rollover threshold — the lowest value of centrifugal acceleration that causes the truck to tip over when driving steadily in a curved path.

A driver doesn’t feel his truck beginning to roll over until after it is too late to respond. The trailer has a higher center of gravity, and its flexibility allows it to twist and start to roll while the tractor’s tires maintain road contact.

Rollovers can occur when a truck is traveling too fast, especially around a curve, when the tires strike something on the roadway while turning, or when the tires go off of the pavement or a truck is returning to the road after drifting off the pavement. Rollovers can also happen due to abrupt lane changes or sudden road maneuvers.

Driver inattention and/or fatigue also play a role. Then there is the influence of a truck’s length, weight, cargo, weight distribution, suspension, center of gravity and so forth. While electronic vehicle stability systems, highway design and signage and automated warning systems can help prevent truck rollovers, the bigger factor is driver behavior and awareness. The most effective way to avoid a rollover, or any accident, is to always drive safely and cautiously.

Stay alert and keep your eyes on the road. Try to anticipate the actions of other drivers, but never presume to know what another driver will do. Avoid sudden maneuvers, such as swerving quickly to avoid hitting an animal or road obstacle.

And as a grizzled long-hauler advised me early on in my trucking career: “Drive the load, not just the road.” He also told me: “Always keep your doors locked to prevent them from opening during a sharp maneuver or an accident.”

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