[Paper] Sports utility vehicles and older pedestrians

Victor

Two guys from TCD have had a paper published in the British Medical Journal

http://bmj.bmjjournals.com/cgi/content/full/331/7520/787?etoc

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Their results show that, for the same collision speed, the likelihood of a pedestrian fatality is nearly doubled in the event of a collision with a large SUV compared with a passenger car.6 Other studies have consistently showing higher rates (up to four times greater) of severe injury and death for pedestrians in collisions with SUVs.7-9

A common misconception is that the increased vehicle mass of SUVs is responsible for the increased hazard to pedestrians. In fact, although vehicle mass is important in car to car collisions, it is a minor factor in vehicle-pedestrian collisions given the disparity between the weights of the pedestrian and of the vehicle.w6 The increased mortality and morbidity from SUVs arises primarily from the geometry of the front end structure. In a typical collision between a car and an adult, the bumper strikes the lower legs and the leading edge of the bonnet strikes the femur/pelvis, causing the pedestrian to rotate towards the bonnet. This results in the bonnet or windscreen hitting the shoulders or head. After this further injuries often occur through impact with the ground. A key mitigating factor in injury severity is the relatively peripheral nature of the primary impact of the bumper to the lower legs.w7-w9 This affords some protection to the critical upper body regions in the primary impact, and the resulting body rotation on to the bonnet tends to further diminish the impact—a characteristic often called "wrap and carry." The principal pedestrian injuries from cars are predominantly fractures of the tibia and fibula and knee injuries from the primary impact with the bumperw10 and head injuries from the secondary impact with the bonnet or windscreen.w11

SUV bonnets are higher than those of cars and this results in a more severe primary impact on the critical central body regions of the upper leg and pelvis.w12 Also, there is less rotation as the impact is closer to the body centre of mass, resulting in a more efficient transfer of energy. For example, raising the bonnet leading edge height from 600 mm to 850 mm increases the impulse by a factor of about two.w13 This results in a doubling of injuries to vulnerable regions such as the head, thorax, and abdomen.9

Another group of vulnerable road users are small children, and a well described risk with SUVs are accidents in driveways, in which SUVs and light trucks are over-represented.w14 w15 This is probably a result of the increased height of the SUV and the driver's reduced ability to see things around the vehicle.


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