Safety systems

From its beginnings, the automobile posed serious hazards to public safety. Vehicle speed and weight provided an impact capacity for occupants and pedestrians that produced great numbers of fatalities (13,000 in 1920) and serious injuries. During the 20th century, the rates of death and injury declined significantly in terms of vehicle miles (in the United States, for example, the rate of fatalities declined from 5.7 to 2.2 per 100,000,000 vehicle miles between 1966 and 1990). Because of the increased number of vehicles on the road, however, total fatalities have declined only slightly (from 53,000 down to 47,000 in the same example period).

Most fatal accidents occur on either city streets or secondary roads. Federal expressway systems are relatively safer. Driver training, vehicle maintenance, highway improvement, and law enforcement were identified as key areas with potential for improving safety, but the basic design of the vehicle itself and the addition of special safety features received increased attention. Safety features of automobiles come under two distinct headings: accident avoidance and occupant protection

Systems for protecting occupants in the event of an accident fall into four major classes: maintenance of passenger-compartment integrity, occupant restraints, interior-impact energy-absorber systems, and exterior-impact energy absorbers. Statistics indicate a far higher chance for survival among accident victims remaining inside the passenger compartment. Passenger-compartment integrity depends significantly on the proper action of the doors, which must remain closed in the event of an accident and must be sufficiently secure to prevent intrusion.

Door-latch mechanisms have been designed to resist forward, rearward, and sideward forces and incorporate two-stage catches, so that the latch may hold if the primary stage fails. Reinforcement beams in doors are designed to deflect impact forces downward to the more rigid frame structure below the door. Forces are directed through reinforced door pillars and hinges.

Occupant restraints are used to help couple the passenger to the car. They permit decelerating with the car rather than free flight into the car structure or into the air. Combination lap- and shoulder-belt systems are the most common restraint system. These consist of web fabrics that are able to withstand 6,000-pound test loading and are bolted to the car underbody and roof rail. Button-type latch release mechanisms are provided for buckles.

Another line of research has centred on passive restraints that do not require any action by the occupant. The air bag is a good example of this concept. It consists of an inflatable cushion that is concealed in the steering column or in areas of the car that are directly in front of passengers. It provides passive crash protection by inflating to a position between occupants and the car structure in less than one-tenth of a second.

The bag absorbs impact energy from occupants as they are thrown forward during a frontal crash. The bag collapses in approximately one second. Energy is absorbed by forcing gas out of the cushion through a series of ports or orifices in the fabric. A crash sensor sends an electrical signal to an igniter which triggers an explosion that generates nitrogen gas to inflate the air bag. It has been estimated that 46 percent of front-seat fatalities could be eliminated by air bags when they are used in conjunction with lap or lap and shoulder belts. This is a 10 percent improvement over lap and shoulder belt systems. The front-mounted air bag does not provide protection in side or rear crashes or in prolonged impacts from rollovers.

II. Look through the text again and answer the following questions:

1. Why do you think the most fatal accidents occur on the city streets and secondary roads?

2. How many classes do the systems for protecting occupants fall into? What are they?

3. What are the most common restraint systems in a car?

4. What restraints do not require any action by the occupant?

5. Do you consider an air bag a real preventer of the front-seat fatalities? Why?

III. Match the words with their definitions and make up your own sentences with these words:

1. impact a) a person, holding a place;

2. research b) some defense, cover or shelter;

3. decline c) an unforeseen event that occurs by chance;

4. occupant d) a system or structure of moving parts;

5. safety e) the ability to control some impulses;

6. accident f) betterment or amelioration;

7. protection g) freedom of danger or risk from injury;

8. restraint h) a careful search in order to discover some facts;

9. mechanism i) the act of one body, object striking another;

10. improvement j) gradual deterioration or loss;

IV. Find information about the function of different kinds of safety systems. While looking for information you are free to use the internet sites given below as well as any other online resources.

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