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. The term "industry standard," however, is ordinarily taken to have a broader meaning, including formal standards as just defined, and also including designs and procedures not required in formal standards, though prevailing in a specific industry, and which represent generally accepted custom and practice.
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.
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.
When a person becomes aware of a dangerous situation, a time-interval must elapse before he can take defensive action against it. This time interval, commonly called the reaction time, has been found to be about 0.7 second 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?
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.
It was a dark and lonely night – as your client, a middle aged man, drove along an unfamiliar country road, watching out for deer that often jump out in front of cars at that time of year. Soon after the road curved to the right he realized that a disabled car with no lights on was angled across the road in front of him.
Back in graduate school, the Psychology Department chair at MIT liked to tell his classes about the three Laws of Nature: the Law of Falling Bricks, the Law of Falling Cats, and the Law of Falling People. Physicists have formulated the precise laws that describe how a brick falls from a table to the floor. Biologists have discovered how cats fall differently from bricks, twisting reflexively to always land on their feet. But what laws completely describe a person falling from a roof? This is the challenge of behavioral scientists.
To err is human; to design is divine. Forensic Human Factors specialists help lawyers analyze the root cause of an accident by determining who erred and why. Human factors applies research from a number of fields to design and evaluate things that people use in work and everyday activities