Roof crush
Encyclopedia
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. The number of occupant injuries is significantly higher. The relationship between injury levels and intrusion or roof crush has been statistically established, 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, but the severity of these events, and thus their potential for causing injury, has been questioned.
Observations from school bus
and heavy truck
rollovers also suggests that the fall and dive theories are incorrect 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". 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.
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 and is currently being reviewed. 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.
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
roof into the passenger compartment during a rollover accident
Rollover
A rollover is a type of vehicle accident in which a vehicle tips over onto its side or roof. The most common cause of a rollover is traveling too fast while turning.- Dynamics :Vehicles can roll over in several ways...
.
Every year approximately 10,000 Americans are killed in rollover
Rollover
A rollover is a type of vehicle accident in which a vehicle tips over onto its side or roof. The most common cause of a rollover is traveling too fast while turning.- Dynamics :Vehicles can roll over in several ways...
accidents, accounting for about 30% of all light vehicle occupant fatalities. The number of occupant injuries is significantly higher. The relationship between injury levels and intrusion or roof crush has been statistically established, 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, but the severity of these events, and thus their potential for causing injury, has been questioned.
Observations from school bus
School bus
A school bus is a type of bus designed and manufactured for student transport: carrying children and teenagers to and from school and school events...
and heavy truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
rollovers also suggests that the fall and dive theories are incorrect 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". 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
Relative velocity
In non-relativistic kinematics, relative velocity is the vector difference between the velocities of two objects, as evaluated in terms of a single coordinate system....
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.
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
Chassis
A chassis consists of an internal framework that supports a man-made object. It is analogous to an animal's skeleton. An example of a chassis is the underpart of a motor vehicle, consisting of the frame with the wheels and machinery.- Vehicles :In the case of vehicles, the term chassis means the...
. The current Federal regulation involving roof strength - 49 CFR 571.216 (FMVSS 216) - has been found to offer little benefit and is currently being reviewed. Many European manufacturers provide stronger roofs than do U.S. or Asian manufacturers despite the fact that there is no European (EEC
EEC
EEC is an abbreviation that usually refers to the European Economic Community, the forerunner to the European Union.It may also refer to;* The East Erie Commercial Railroad, a shortline in Pennsylvania...
) roof strength regulation for light vehicles. The Volvo XC90
Volvo XC90
The Volvo XC90 is a mid-size luxury crossover SUV produced by Volvo Cars since it was unveiled at the Detroit Motor Show 2002. It is based on the P2 platform, shared with the first generation Volvo S80 and other large Volvo cars...
may be a good example of this.