The second type of collision is the side impact. In fatal crashes involving passenger cars, it is second in frequency to front impacts. These crashes usually occur at intersections when a car is struck broadside by another vehicle going through the intersection at right angles to the first. In such cases, dicing injuries can be found on either one or both sides of a driver, depending on whether the side glass is propelled into the driver; the driver into the glass, or both. Side impact crashes can also occur when a car skids sideways, striking a fixed object such as a tree or pole with its side.
In car-to-car collisions, where the impact is to the driver's side, force is applied from the shoulder level downward. The head can flex laterally through the side window, striking the impacting vehicle. It might also impact the A or B pillars. If the impacting vehicle is a truck, the force is delivered from roof to floor level, and the intruding vehicle can make direct contact with the head. A seatbelt or frontal airbag in this situation yields virtually no benefit. External injuries — abrasions, lacerations, dicing injuries, and fractures — will tend to be on the left side of the body, and the
left arm and leg may be fractured. Internally, fractures of the ribs tend to be predominantly on the left side. While textbooks always discuss transections of the aorta from head-on collisions, these injuries can result from a side impact as well. In addition, there might be rupture of the heart, with the same type of injuries as those in head-on collisions. Lacerations of the liver and, to a lesser degree, the spleen, can be present, as well as lacerations of the left kidney. Basilar fractures and fractures of the neck might occur. The overall impression with such cases, however, is that the injuries to the left side of the body are more severe than the right. In the case of passengers in this vehicle, the injuries will tend to be to the left side. Unrestrained front seat passengers might be cushioned by the driver, reducing the severity of the injuries to some degree. Use of a seatbelt by the passenger can reduce the severity of or even eliminate injuries by preventing the passenger from making contact with the driver, the impacting vehicle, or structures in the passenger compartment.
If the impact is from the right (i.e., the passenger's) side, the injuries will tend to be more severe on the right side of the body. Transection of the aorta may occur, though it is less common than from front or left-side impacts. Lacerations of the heart, liver, and spleen; fractures of the neck; and basal fractures can also occur.
As noted, seat belts tend to keep people in place rather than having them hurled from one side of the vehicle to the other. They are less effective in preventing injuries in side impacts than in head-on crashes, because the sides of motor vehicles are constructed of thin sheet metal.
When a side impact occurs, fatalities usually occur in the car impacted rather than the car impacting, because the engine protects the impacting driver and passengers. In side impact collisions with fixed objects, that is, when a car slides sideways into a fixed object, the driver or a passenger if not restrained may partially pop out the window, impact the fixed object, and then pop back into the vehicle.
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