C H A P T E R 1
1.1 WHAT IS VEHICLE ROLLOVER?
Vehicle rollover is a dangerous lateral movement which refers to the vehicle in the process of
driving around its longitudinal axis rotate 90
or more, so that the body is in contact with the
1.2 RISK OF VEHICLE ROLLOVER ACCIDENTS
Vehicle rollover accidents have been a serious safety problem for the last three decades. Athough
rollovers are a small percentage of all traﬃc accidents, they do account for a large propor-
tion of severe and fatal injuries. According to National Highway Traﬃc Safety Administration
(NHTSA) in the U.S., rollover accidents are the second most dangerous form of accident in
the U.S., after head-on collisions. In 2012, almost 5.615 million vehicles crashed in the U.S.,
although only 2.0% involved vehicle rollover, and the proportion of vehicles that rolled over
in fatal crashes was 20.3% . Speciﬁcally, some large passenger vehicles are more prone to
rollover accidents with a high center of gravity (CG) and narrow track width such as large vans,
pickup trucks, and sport utility vehicles. erefore, rollover prevention is important for vehicle
dynamics and active safety .
1.3 FACTORS AFFECTING VEHICLE ROLLOVER
Vehicle rollover accidents may be grouped into two categories: tripped and untripped rollovers.
A tripped rollover commonly occurs when a vehicle skids and digs its tires into soft soil or hits a
tripping mechanism such as a curb with a suﬃciently large lateral velocity. On the other hand,
the untripped rollover is induced by extreme maneuvers during critical driving situations, such
as excessive speed during cornering, obstacle avoidance, and severe lane change maneuver. In
these situations, the forces at the tire-road contact point are enough to cause the vehicle to roll
over. Furthermore, vehicle rollover can occur during external disturbances such as side-wind
and steering excitation. ere is a good body of work in untripped rollovers while studies in
tripped rollovers are relatively limited although crash data show that the majority of rollover
accidents are tripped rollovers . e reason is that tripped rollovers are more complex, and
their dynamics are more complicated and less understood.