![]() ![]() Light trucks will roll over at lateral accelerations of 0.8 to 1.2 g. The Tesla Model S has an unusually low rollover risk of 5.7% due to its low center of mass. The rollover threshold for passenger cars is over 1 g of lateral acceleration. Generally, rollover tendency increases with the height of the center of mass, narrowness of the axle track, steering sensitivity, and increased speed. Vehicles exiting a wind shadow can be subjected to instant gusts that can affect high-sided vehicles.Īll vehicles are susceptible to rollovers to various extents. Risk areas are coastal roads, plains and exposed bridges. Strong winds may cause high-sided vehicles such as trucks, buses and vans to be blown over. A trailer jackknife can push the towing vehicle into a rollover scenario if the vehicle is subject to a tripped scenario (soft ground or a curb). A vehicle may roll over when hitting a large obstacle with one of its wheels or when maneuvering over uneven terrain. Slopes steeper than 33% (one vertical unit rise or fall per three horizontal units) are called "critical slopes" because they can cause most vehicles to overturn. Ī rollover can also occur as a vehicle crosses a ditch or slope. In 1983, crash tests showed that light trucks were prone to rolling over after colliding with certain early designs of guide rail. The tires resist the change, and the coupled forces rotate the vehicle. ![]() A side impact can accelerate a vehicle sideways. Turned down guard rail end sections have been shown to do this. These occur when the collision causes the vehicle to become unstable, such as when a narrow object causes one side of the vehicle to accelerate upwards, but not the other. Īnother type of tripped rollover occurs due to a collision with another vehicle or object. In a 2003 report, this was the most common mechanism, accounting for 71% of single-vehicle rollovers. The physics are similar to cornering rollovers. The most common type of tripped rollover in light passenger vehicles occurs when a vehicle is sliding sideways, and the tires strike a curb, dig into soft ground, or a similar event occurs that results in a sudden increase in lateral force. When the tire and inertial forces are enough to overcome the force of gravity, the vehicle starts to turn over. ![]() The force of the vehicle's weight acts downward through the center of mass in the opposite direction. These two forces make the vehicle roll towards the outside of the curve. The force of inertia acts horizontally through the vehicle's center of mass away from the center of the turn. This force acts at ground level, below the center of mass. The cornering forces from the tire push the vehicle towards the center of the curve. As a vehicle rounds a corner, three forces act on it: tire forces (the centripetal force), inertial effects (the centrifugal force), and gravity. Untripped rollovers occur when cornering forces destabilize the vehicle. those that use a trailer coupling rather than a fifth wheel) are more prone to rolling as they do not have the tractor unit or prime mover for additional stability. Untripped rollovers are the result of steering input, speed, and friction with the ground. ![]() Tripped rollovers are caused by forces from an external object, such as a curb or a collision with another vehicle. Vehicle rollovers are divided into two categories: tripped and untripped. ![]()
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