Persons with no training in engineering are generally unaware of the nature of engineering analysis, and so tend to assume that testing, as a means of determining the causation of accidents, is a dominant tool of the engineer. In the following examples, we shall undertake to explain the nature of engineering analysis, and to show that it is more basic than testing because testing without analysis is meaningless. Further, while analysis is always necessary in accident reconstruction, testing is only sometimes necessary.
The following are original articles written by the Technology Associates staff. Though they do not encompass all our areas of expertise, they provide some detailed information about some of the common types of accidents we encounter on a regular basis. They also provide references to articles written by our engineers that have been published in peer-reviewed scientific journals.
Accident reconstructionists are often called on to determine the distance that a car, covers while being braked to a stop. Conversely, the reconstructionist may be given information as to the length of the skidmarks left by a car on the roadway, and may be asked to determine how fast the car must have been going at the beginning of the skid. An expert can accomplish this with considerable accuracy, based on a knowledge of the physical principles that are involved, plus available information relating to the friction of tires on various types of road surfaces.
When a person becomes aware of a dangerous situation, some time will elapse before he can take evasive or defensive action against it. This time interval, commonly called the reaction time, has been found to be about 0.7 seconds for all normal persons, regardless of their background and training. This suggests that the reaction time depends on some basic aspect of the human physiology-involving the brain, nervous system, and muscles-which does not vary much from person to person.
A car is stopped for a light when it is unexpectedly rear-ended by a vehicle from behind. It is not a hard impact and there is little or no damage to either vehicle, because the energy absorbing bumpers have protected them. Nevertheless, the passengers of the struck vehicle complain of neck, shoulder and back pain. The next day they allegedly experience even greater pain and visit a medical person who claims that they have been injured. Insurance claim representatives, attorneys, medical, engineering and biomedical experts are then brought in and various conflicting allegations, testimony and opinions are expressed. Do we have a legitimate injury claim on our hands or a situation of fraud?
Vehicle impact severity has been used to infer whiplash injury to asymptomatic, healthy occupants during low-speed, rear-end collisions. However, vehicles speeds at impact are sometimes difficult to determine because existing crush formulas are not always applicable over certain ranges of closing speed. An alternative method for determining impact speed and severity that has been pioneered by Technology Associates to determine accident severity in those cases
Second to automobile accidents, accidents due to falls are the leading cause of injury and death. Of these, accidents due to slipping (not tripping) form a large proportion. Slipping may occur on floors, walkways, and stairs or steps. For Introductory purposes, however, the present discussion will be limited to slipping on flat surfaces such as a floor or sidewalk.
According to Consumer Product Safety Commission (CPSC) accident estimates, tens of thousands of stepladder accidents requiring emergency room treatment occurred annually in the United States. Approximately 85-90% of these accidents involve the user falling from the ladder and 8-9% of these injuries are serious enough to require that the victim be admitted to a hospital. In addition to posing a severe health concern, these accidents have significant loss-of-wages and high medical expense implications
Golf cart rollovers often occur as a result of a driver losing control of the car while traveling downhill on a car path. One potential source of a downhill loss of control is the current industry practice of manufacturing golf carts with brakes on only the rear axle wheels. It has long been understood that a braked vehicle with skidding rear tires and rolling front tires is directionally unstable but this instability will not always manifest itself when a vehicle is traveling at sufficiently low speeds on level ground.
According to the Consumer Products Safety Commission (CPSC), there are approximately 15,000 golf car related injuries requiring emergency room treatment in the US each year.
One significant mode of injury in golf car accidents is passenger ejection, which can lead to serious injuries, especially of the head.
A standard can be defined as a document issued by a recognized agency, and dealing with design and/or safety requirements relating to a specific product or type of activity. Such agencies include the U.S. Occupational Safety and Health Administration (051-IA) and the American National Standards Institute (ANSI). OSHA standards are generally legally binding for an employer, while ANSI standards are generally of an advisory nature.
At first thought it would seem that the hazards of operating a dangerous machine should be apparent to the average person, so that, if an accident occurs, it must be due to his own negligence. For example, if a machine for shearing thick stacks of paper contains a large knife that descends forcefully when a foot pedal is pressed, one might expect that common sense would lead the operator to keep his hands out of the danger zone. Again, in a machine that has exposed gearing, common sense should serve to warn the operator to keep his hands-and his clothing-away from the gear teeth. If a printing press has two rollers which are in forceful contact and which rotate together in such a way as to create an “ingoing nip point” at their line of contact, it would seem that the operator’s protective instincts should suffice to keep his fingers away from the nip point.
What must a warning sign accomplish? First, it must inform a worker, or user or owner of a machine, of the dangers that would not be obvious to him. Second, it must tell him how to avoid the danger. Third, it must be easily understood.