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Roof crush is the failure and displacement of an automobile roof into the passenger compartment during a rollover accident.
Every year approximately 10,000 Americans are killed in rollover accidents, accounting for about 30% of all light vehicle occupant fatalities. [1] The number of occupant injuries is significantly higher. The relationship between injury levels and intrusion or roof crush has been statistically established, [2] but the mechanism has been thought sometimes to be somewhat obscure. Theories advocating the idea that rollover injuries are caused by the occupants "falling" or "diving" into the vehicles interior have been advanced, [3] but the severity of these events, and thus their potential for causing injury, has been questioned. [4]
Observations from school bus and heavy truck rollovers also suggests that the fall and dive theories are incorrect [5] and that another theory of the mechanism of injury in rollover accidents is required, one that relates injury to the intrusion of the roof structure into the occupant compartment or more simply to "roof crush". [6] Today it is generally realized that the primary injury mechanism in light vehicle rollover accidents is not crushing. Rather, it is widely acknowledged that the principal injury process for contained, i.e., non-ejected, occupants involves the impact between the occupant and the vehicle interior. Since the severity of an impact depends to a large extent on the relative velocity between the impacting objects; the impact theory of injury causation in rollovers has sought to explain the increase in injuries associated with increased roof crush with an increase in the relative velocity between the occupant and the vehicle's interior which is generated by the roof crush. In the simplest terms, when the occupants hits a collapsing roof, they hit harder because the roof is moving in on them. If the roof was not collapsing, and thus moving towards the occupants, their velocity relative to the roof would be lower and the impact less severe.[ citation needed ]
Roof crush has also been identified as a cause of both full and partial ejection in rollover accidents because of ejection portals created by the collapsing roof structure. These chiefly involve broken windows but occasionally also involve the body structure. The current Federal regulation involving roof strength - 49 CFR 571.216 (FMVSS 216) - has been found to offer little benefit [7] and is currently being reviewed. [8] Many European manufacturers provide stronger roofs than do U.S. or Asian manufacturers despite the fact that there is no European (EEC) roof strength regulation for light vehicles. The Volvo XC90 may be a good example of this. [9]
A seat belt is a vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt reduces the likelihood of death or serious injury in a traffic collision by reducing the force of secondary impacts with interior strike hazards, by keeping occupants positioned correctly for maximum effectiveness of the airbag and by preventing occupants being ejected from the vehicle in a crash or if the vehicle rolls over.
An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. The purpose of the airbag is to provide a vehicle occupant with a soft cushioning and restraint during a crash event. It can reduce injuries between the flailing occupant and the interior of the vehicle.
A crash test dummy is a full-scale anthropomorphic test device (ATD) that simulates the dimensions, weight proportions and articulation of the human body during a traffic collision. Dummies are used by researchers, automobile and aircraft manufacturers to predict the injuries a person might sustain in a crash. Modern dummies are usually instrumented to record data such as velocity of impact, crushing force, bending, folding, or torque of the body, and deceleration rates during a collision. Some dummies cost over US$400,000.
Crumple zones, crush zones, or crash zones, are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity occurs from the impact during a collision by controlled deformation; in recent years also incorporated into trains and railcars.
A crash test is a form of destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibility for various modes of transportation or related systems and components.
Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design.
A bumper is a structure attached to or integrated with the front and rear ends of a motor vehicle, to absorb impact in a minor collision, ideally minimizing repair costs. Stiff metal bumpers appeared on automobiles as early as 1904 that had a mainly ornamental function. Numerous developments, improvements in materials and technologies, as well as greater focus on functionality for protecting vehicle components and improving safety have changed bumpers over the years. Bumpers ideally minimize height mismatches between vehicles and protect pedestrians from injury. Regulatory measures have been enacted to reduce vehicle repair costs and, more recently, impact on pedestrians.
A rollover is a type of vehicle crash in which a vehicle tips over onto its side or roof. Rollovers have a higher fatality rate than other types of vehicle collisions.
The Insurance Institute for Highway Safety (IIHS) is a U.S. nonprofit organization funded by auto insurance companies, established in 1959 and headquartered in Arlington, Virginia. It works to reduce the number of motor vehicle traffic collisions, and the rate of injuries and amount of property damage in the crashes that still occur. It carries out research and produces ratings for popular passenger vehicles as well as for certain consumer products such as child car booster seats. It also conducts research on road design and traffic regulations, and has been involved in promoting policy decisions.
Side collisions are vehicle crashes where the side of one or more vehicles is impacted. These crashes often occur at intersections, in parking lots, and when two vehicles pass on a multi-lane roadway.
Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different criteria are used to determine the crashworthiness of the structure. Crashworthiness may be assessed either prospectively, using computer models or experiments, or retrospectively by analyzing crash outcomes. Several criteria are used to assess crashworthiness prospectively, including the deformation patterns of the vehicle structure, the acceleration experienced by the vehicle during an impact, and the probability of injury predicted by human body models. Injury probability is defined using criteria, which are mechanical parameters that correlate with injury risk. A common injury criterion is the Head impact criterion (HIC). Crashworthiness is assessed retrospectively by analyzing injury risk in real-world crashes, often using regression or other statistical techniques to control for the myriad of confounders that are present in crashes.
Federal Motor Vehicle Safety Standards (FMVSS) are U.S. federal regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated Automobile safety-related components, systems, and design features. They are the U.S. counterpart to the UN Regulations developed by the World Forum for Harmonization of Vehicle Regulations and recognized to varying degree by most countries except the United States. Canada has a system of analogous rules called the Canada Motor Vehicle Safety Standards (CMVSS), which overlap substantially but not completely in content and structure with the FMVSS. The FMVSS/CMVSS requirements differ significantly from the international UN requirements, so private import of foreign vehicles not originally manufactured to North American specifications is difficult or impossible.
A traffic collision, also called a motor vehicle collision (MVC) among other terms, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction, such as a tree, pole or building. Traffic collisions often result in injury, disability, death, and property damage as well as financial costs to both society and the individuals involved.
When a person makes a claim for personal injury damages that have resulted from the presence of a defective automobile or component of an automobile, that person asserts a product liability claim. That claim may be against the automobile's manufacturer, the manufacturer of a component part or system, or both, as well as potentially being raised against companies that distributed, sold or installed the part or system that is alleged to be defective.
Worldwide it was estimated that 1.25 million people were killed and many millions more were injured in motor vehicle collisions in 2013. This makes motor vehicle collisions the leading cause of death among young adults of 15–29 years of age and the ninth cause of death for all ages worldwide. In the United States, 40,100 people died and 2.8 million were injured in crashes in 2017, and around 2,000 children under 16 years old die every year. It is estimated that motor vehicle collisions caused the deaths of around 60 million people during the 20th century, around the same as the number of World War II casualties.
A crush injury is injury by an object that causes compression of the body. This form of injury is rare in normal civilian practice, but are common following a natural disaster. Other causes include industrial accidents, road traffic collisions, building collapse, accidents involving heavy plant, disaster relief or terrorist incidents.
Plug-in electric vehicle fire incidents have taken place between the introduction of mass-production plug-in electric vehicles in 2010 and 2014, when the battery type was changed to nickel-metal hydride batteries which do not pose the same risk of thermal runaway as lithium-ion batteries. As a result of these incidents, the United States, Department of Transportation's National Highway Traffic Safety Administration (NHTSA) conducted a study to establish whether lithium-ion batteries in plug-electric vehicles pose an exceptional fire hazard. The research looked at whether the high-voltage batteries can cause fires when they are being charged, and when the vehicles are involved in an accident.
Regarding the risk of electrochemical failure, [this] report concludes that the propensity and severity of fires and explosions from the accidental ignition of flammable electrolytic solvents used in Li-ion battery systems are anticipated to be somewhat comparable to or perhaps slightly less than those for gasoline or diesel vehicular fuels. The overall consequences for Li-ion batteries are expected to be less because of the much smaller amounts of flammable solvent released and burning in a catastrophic failure situation.
The flail space model (FSM) is a model of how a car passenger moves in a vehicle that collides with a roadside feature such as a guardrail or a crash cushion. Its principal purpose is to assess the potential risk of harm to the hypothetical occupant as he or she impacts the interior of the passenger compartment and, ultimately, the efficacy of an experimental roadside feature undergoing full-scale vehicle crash testing.
Federal Motor Vehicle Safety Standard 226 regulates automotive ejection mitigation in the United States. Like all other Federal Motor Vehicle Safety Standards, FMVSS 226 is administered by the United States Department of Transportation's National Highway Traffic Safety Administration.
Charles Adrian Hobbs is a safety expert in vehicle crashworthiness with a background in accident and injury investigation, and analysis.
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