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Lessons Learned:
How to Prevent Rollovers
NEWS FLASH — A truck carrying
hazardous materials on I-99 overturned on the westbound
ramp to Kona, Hawaii...How many times have you heard
a report like this on the radio and held your breath
hoping it wasn’t one of your fleet’s vehicles!
The good news is that rollovers can be prevented! Drivers
must be educated in the factors that contribute to rollovers
and trained in how to prevent them.
Driver Training
Start by training your drivers in the four important
factors that contribute to vehicle stability. These
are:
- Vehicle Center Of Gravity — The height of
a vehicle’s center of gravity and the length
of the wheel base determine the vehicle’s stability.
Picture a vertical line that shifts to the right or
left as the vehicle rounds curves or travels on a
banked roadway. A rollover occurs when this imaginary
line passes outside the vehicle’s wheel base.
- Radius Of Curves And Slope Of Roadways —
Both are important because they generate a centrifugal
force that acts sideways from the center of gravity.
The centrifugal force increases the angle of the aforementioned
vertical line from the center of gravity, thereby
decreasing vehicle stability.
- Load Security — Improperly secured loads
can change a vehicle’s center of gravity and
its stability. Bulk tank trucks are inherently less
secure because fluids can surge when trucks brake
or round curves, thereby altering the center of gravity.
However, a vehicle loaded with building materials
(i.e., stacked lumber) will have a similar high center
of gravity.
- Vehicle Speed — This is probably the most
important factor contributing to vehicle instability
because it magnifies problems presented by the other
three factors. As the vehicle’s speed increases,
the centrifugal force increases in an amount equal
to the square of the vehicle’s speed. Faster
speeds also result in decreased driver response times.
Speed is the factor over which the driver can exercise
the most control.
When maneuvering through curves or sudden traffic situations,
a vehicle with a high center of gravity can easily turn
over. Speed is even more important when the movement
of the liquid is “in phase” with the vehicle’s
maneuver. If the liquid is on one side during the first
curve, then shifts to the other side during the next
curve, the liquid is positioned to shift back to the
first side with four times the side force it had during
the initial curve. A sudden evasive maneuver has not
only three forces, but it combines the side force with
the forward liquid surge that results in a great lift
of the vehicle from the roadway — and the potential
for a rollover.
What Can The Individual Driver Do?
Fortunately, every driver can take six basic steps
to prevent or minimize the potential for rollovers.
Make these steps a company policy and train your drivers
on them. Retraining and reinforcement of these steps
will show how important safety is to your company:
- Adjust the vehicle speed to allow a “Speed
Cushion” for maneuvering (at least 10 MPH below
the posted speed limit is recommended) when approaching
a curve.
- Slow down and downshift early. Don’t shift
in the curve.
- Look at both the speed limit sign and your speedometer
to ensure that your vehicle is below the posted speed.
- Don’t rely on a “seat of the pants”
sense to judge speed and vehicle maneuverability.
New suspensions and chassis set-ups give a false sense
of control.
- Slowly accelerate out of the curve.
- Maintain a “Space Cushion” (distance
between your vehicle and other traffic) so that you
have a safe maneuvering speed necessitated by your
misjudgment, weather and road conditions, and poor
driving by other motorists.
Remember, driver education and accident prevention
are necessary to avoid loss of life, serious employee
injury and costly spill response scenarios.
XL Environmental • Risk Control Division •
505 Eagleview Boulevard, PO Box 636, Exton, PA 19341
• Phone: 800-327-1414 • Fax: 610-458-7285
• xlenvironmental.com
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