Editing Vehicle rollover (section)

==Dynamics==
[[File:Indonesian fire fighters during a traffic accident.jpg|thumb|A rolled over [[Box truck]] being handled by [[fire fighters]] in [[Jakarta]], [[Indonesia]]]]
Vehicle rollovers are divided into two categories: tripped and untripped. Tripped rollovers are caused by forces from an external object, such as a curb or a collision with another vehicle. Untripped rollovers are the result of steering input, speed, and friction with the ground.<ref>{{cite web |url=http://www.its.umn.edu/Publications/ResearchReports/pdfdownload.pl?id=2206 |title=Prediction and Prevention of Tripped Rollovers |author=Gridsada Phanomchoeng and Rajesh Rajamani |publisher=Department of Mechanical Engineering, University of Minnesota |date=December 2012 |access-date=2013-02-05 |archive-date=2020-07-05 |archive-url=https://web.archive.org/web/20200705150518/http://www.its.umn.edu/Publications/ResearchReports/pdfdownload.pl?id=2206 |url-status=dead }}</ref> Trailers that are not roll-coupled (i.e. 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===
Untripped rollovers occur when cornering forces destabilize the vehicle. As a vehicle rounds a corner, three forces act on it: tire forces (the [[centripetal force]]), inertial effects (the [[centrifugal force]]), and [[gravity]]. The cornering forces from the tire push the vehicle towards the center of the curve. This force acts at ground level, below the center of mass. The force of [[inertia]] acts horizontally through the vehicle's center of mass away from the center of the turn. These two forces make the vehicle roll towards the outside of the curve. The force of the vehicle's weight acts downward through the center of mass in the opposite direction. When the tire and inertial forces are enough to overcome the force of gravity, the vehicle starts to turn over.

===Tripped 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. The physics are similar to cornering rollovers. In a 2003 report, this was the most common mechanism, accounting for 71% of single-vehicle rollovers.<ref>{{cite web |url=https://crashstats.nhtsa.dot.gov/Api/Public/Publication/809692 |title=Examination of Rollover Crash Mechanisms and Occupant Outcomes |publisher=National Highway Transportation Safety Administration |year=2003 }}</ref>

Another type of tripped rollover occurs due to a collision with another vehicle or object. 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. Turned down [[guard rail]] end sections have been shown to do this. A side impact can accelerate a vehicle sideways. The tires resist the change, and the coupled forces rotate the vehicle. In 1983, [[crash test]]s showed that light trucks were prone to rolling over after colliding with certain early designs of guide rail.<ref>{{cite web |url=http://engineering.unl.edu/specialty-units/MWRSF/MwRSF-Downloads/MGS/TRR%202025%20Paper%2007-2642.pdf |title=Performance of Steel-Post, W-Beam Guardrail Systems (Paper No. 07-2642) |access-date=2009-04-23 |url-status=dead |archive-url=https://web.archive.org/web/20100605004632/http://engineering.unl.edu/specialty-units/mwrsf/MwRSF-Downloads/MGS/TRR%202025%20Paper%2007-2642.pdf |archive-date=2010-06-05 }} Kaller, Sicking et al, Performance of Steel-Post, W-Beam Guardrail Systems, 2007,</ref>

A rollover can also occur as a vehicle crosses a ditch or slope. 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.<ref>{{cite book |title=Roadside Design Guide |publisher=American Association of State Highway Transportation Officials |date=2002 |pages=3–13}}</ref> A vehicle may roll over when hitting a large obstacle with one of its wheels or when maneuvering over uneven terrain. A trailer [[jackknifing|jackknife]] can push the towing vehicle into a rollover scenario if the vehicle is subject to a tripped scenario (soft ground or a curb).

Strong winds may cause high-sided vehicles such as trucks, buses and vans to be blown over.<ref>{{cite web|url=https://www.driverknowledgetests.com/resources/how-do-rollover-accidents-happen-and-what-causes-them/|title=How do rollover accidents happen and what causes them|date=24 March 2021 }}</ref> Risk areas are coastal roads, plains and exposed bridges.<ref>{{cite journal|title=Wind speed trends over the contiguous United States|year=2009|doi=10.1029/2008JD011416|last1=Pryor|first1=S. C.|last2=Barthelmie|first2=R. J.|author2-link=Rebecca Barthelmie|last3=Young|first3=D. T.|last4=Takle|first4=E. S.|last5=Arritt|first5=R. W.|last6=Flory|first6=D.|last7=Gutowski|first7=W. J.|last8=Nunes|first8=A.|last9=Roads|first9=J.|journal=Journal of Geophysical Research|volume=114|issue=D14|bibcode=2009JGRD..11414105P|s2cid=54761873 |doi-access=free}}</ref> Vehicles exiting a [[windbreak|wind shadow]] can be subjected to instant gusts that can affect high-sided vehicles.