ISSN 1081-4140
SAFET Y BULLETIN
MECHANICAL ENGINEERING:
October 1997
Officers
Ralph L. Barnett
Dolores Gildin
S. Carl Uzgiris
Mechanical Engineering
Dennis B. Brickman
Michael A. Dilich
Christopher W. Ferrone
Suzanne A. Glowiak
John M. Goebelbecker
Crispin Hales
Dror Kopernik
Woodrow Nelson
Peter J. Poczynok
Audrone M. Stake
William G. Switalski
James R. Wingfield
Library Services
Marna Forbes
Betty Bellows
Maureen Vela
Jan A. King
Norene Kramer
Florence Lasky
Neil Miller
Susan Ottlinger
Sandra Prieto
Jackie Schwartz
Peter Warner
Volume 6, No. 1
Triodyne Inc.
Triodyne Inc. (Est. 1969)
Triodyne Recreation
Engineering, Inc. (Est. 1994)
Consulting Engineers & Scientists – Safety Philosophy & Technology
5950 West Touhy Avenue Niles, IL 60714-4610 (847) 677-4730
FAX: (847) 647-2047
VEHICLE SAFETY
Truck Rollover
Engineering/Science
Brian D. King
Jeffery W. Abendshien
Patrick M. Brinckerhoff
Peter J. Poczynok
by Michael A. Dilich1 and John M. Goebelbecker 2
SAFETY RESEARCH:
ABSTRACT
Institute for Advanced
Safety Studies (Est. 1984)
The ability of a heavy truck to successfully negotiate a curve depends upon the
vehicle’s speed, its loaded stability and the geometry of the curve. When a rollover
occurs, evaluation of factors related to the driver, the vehicle, and the roadway is
required.
Alliance Tool & Mfg. Inc.
(Est. 1945)
91 East Wilcox Street
Maywood, IL 60153-2397
(312) 261-1712
(708) 345-5444
FAX: (708) 345-4004
Officers
S. Carl Uzgiris
Ralph L. Barnett
General Manager
Ramesh Gandhi
Plant Manager
Ray Gach
Founders/Consultants
Joseph Gansacz
Albert Kanikula
Video Services
Andrew B. Cizmar
Graphic Communications
Andrew B. Cizmar
Charles D’Eccliss
Model Laboratory
2721 Alison Lane
Wilmette, IL 60091-2101
Bill Brown
Mario Visocnik
Vehicle Laboratory
Charles Sinkovits
Photographic Laboratory
7903 Beckwith Road
Morton Grove, IL 60053
Larry Good
CONSTRUCTION:
Triodyne-Wangler
Construction Company Inc.
(Est. 1993)
Business Systems
Chris Ann Gonatas
Sandie Christiansen
Peggy Dietrich
Sandra M. Duffy
5950 West Touhy Avenue
Niles, IL 60714-4610
(847) 647-8866
FAX: (847) 647-0785
FIRE AND EXPLOSION:
Officers/Directors
John A. Campbell
Ralph L. Barnett
S. Carl Uzgiris
Engineering
John A. Campbell
Scott M. Howell
Norbert R. Orszula
Kim R. Mniszewski
5950 West Touhy Avenue
Niles, IL 60714-4610
(847) 647-1101
Chairman of the Board
Ralph L. Barnett
Director of Operations
Paula L. Barnett
Information Services
Marna Forbes
Senior Science Advisor
Theodore Liber
MANUFACTURING:
Training and Editorial Services
Paula L. Barnett
2907 Butterfield Road
Suite 120
Oak Brook, IL 60521-1176
(630) 573-7707
FAX: (630) 573-7731
5950 West Touhy Avenue
Niles, IL 60714-4610
(847) 647-9882
FAX: (847) 647-0785
Officers/Directors
Brian D. King
Jeffery W. Abendshien
Ralph L. Barnett
S. Carl Uzgiris
e-mail: [email protected]
Information Products
Expert Transcript
Center (ETC)
Marna Forbes
Glenn Werner
Triodyne Fire &
Explosion Engineers, Inc.
(Est. 1987)
RECREATION ENGINEERING:
THE PHYSICS OF ROLLOVER
When a truck travels in a curved path, it leans to the outside of the curve (See Fig.
1). This leaning is caused by the centrifugal force acting through the truck’s center
of gravity. The truck will roll over away from the center of the curve if the centrifugal
force is sufficiently large. The centrifugal force increases with speed and with the
curvature of the road.
The measure of a truck’s ability to resist rollover is given by its rollover threshold.
The rollover threshold is the lowest value of centrifugal acceleration which causes
the truck to tip over when driven steadily in a curved path. One survey of test data
found the rollover thresholds of heavy trucks in the 0.25 to 0.5 g range. Trucks with
lower payloads (lower centers of gravity) and stiffer suspensions have higher
rollover thresholds and are more difficult to roll over in a curve.
When the rollover threshold becomes sufficiently large, the vehicle will have a
tendency to slide out of a curve rather than roll over. For example, automobiles
have this tendency because of their low centers of gravity.
1
Principal Mechanical Engineer, Triodyne Inc., Niles, IL.
2
Project Engineer, Triodyne inc., Niles, IL.
© Copyright 1997 Triodyne Inc.
Officers/Directors/Managers
Joel I. Barnett
William A. Wangler
Joseph Wangler
Ralph L. Barnett
S. Carl Uzgiris
CONSULTANTS:
Richard M. Bilof, Ph.D.
Electromagnetic Compatability
Claudine P. Giebs, M.S.
Biomechanics
Richard Gullickson
Industrial Hygiene/Safety/Chemistry
Beth A. Hamilton
Information Science
David W. Levinson, Ph.D.
Senior Metallurgical Advisor
Steven R. Schmid, Ph.D.
Food Processing Equipment
Center of Gravity
Centrifugal Force
V
h
W
Fig. 1
DISCUSSION
POSSIBLE CONTRIBUTING FACTORS
Truck rollovers typically occur at exit and entrance
ramps of expressways when a driver misjudges the
sharpness of a ramp curve and enters it at an excessive
speed. Drivers of semi’s who have survived rollover
accidents indicate that they did not perceive they were
rolling until they looked in their side view mirrors and saw
the trailer wheels on the inside of the curve lift off
the ground. Then, suddenly, the tractor tipped. The
delayed rolling of the tractor is due to the higher center
of gravity of the trailer and the flexibility of the
trailer structure which allows the trailer to twist and begin
rolling while the tractor wheels maintain contact with the
road.
Driver Factors to Consider:
Entered curve at excessive speed.
Not aware of tractor/trailer limitations.
Did not anticipate sharpness of curve.
Steered truck onto soft shoulder.
Drifted off road and abruptly countersteered.
Did not comply with speed advisory.
Accelerated through curve.
Inexperienced transporting high center of gravity
loads.
Steered abruptly, perhaps during avoidance maneuvers.
Was impaired by fatigue, drowsiness, alcohol,
drugs, poor eyesight, etc.
Was reckless, angry, emotional, or otherwise upset.
Rollover accident victims also often recall sensing that
their load shifted and believe the load shift caused their
accident. However, the load will always shift due to the
extreme tilting of the trailer that occurs during the rollover
event itself. Load shifting during a rollover accident is
typically a result and not the cause of the accident.
When a rollover accident occurs, a number of factors
related to the vehicle, the driver and/or the highway must
be investigated before the cause(s) of the accident can
be determined.
The following list of possible contributing factors was
developed as an aid to the investigation of such accidents.
Vehicle Factors to Consider:
Unusually top heavy load.
Collapsed suspension.
Under-inflated tires.
Poor brake performance prior to entering curve.
Cargo distribution.
Load shift.
Highway Factors to Consider:
Speed advisory for curve.
Superelevation (banking).
Transition curvature.
Shoulder condition.