Introduction to automotive safety

Automotive safety is not a recent invention of Washington legislators. Safety has always been a concern of automakers, even before Federal standards were initiated.

As far back as 1900, when cars were still "horseless carriages," the steering wheel replaced the rudder-like steering stick, adding safety as well as convenience to the car.

In the next decade, the industry introduced the all-steel body, rearview mirror, shock absorbers and the electric horn.

Automobiles of the 1920s were revolutionized by steel wheels, twin-beam headlights, laminated windshield glass, hydraulic brakes on all four wheels, balloon tires and windshield wipers.

The 1930s brought improved steering gears, power brakes, defrosters and sealed-beam headlights.

In the 1940s double hood latches, padded instrument panels, and self-adjusting brakes were first used, in addition to one of the most important safety innovations--the turn signal.

In the post-war 1950s, the population of automobiles increased dramatically and safety became even more important. Seatbelts, head restraints, energy-absorbing steering wheels and impact-resistant door latches were added to most new cars.

The '60s and '70s saw the advent of dual braking systems, collapsible steering columns, wear indicators for various parts of the car, side impact door beams, warning lights and buzzers, seat-belt interlock systems and energy-absorbing bumper systems.

The '80s and '90s brought the addition of improved safety belts, improved side impact protection, head restraints, infant and child seats, and air bag systems. Also, there was a new focus on crash avoidance with the addition of anti-lock brakes and daytime running lights.

There are currently over 60 National Highway Traffic and Safety Administration (NHTSA) standards that directly affect car safety, with more (including revised air bags, improved head restraints, and advanced crash avoidance systems) sure to make it onto the books in the coming years.

Most of the cost of regulatory compliance has been passed on to the consumer in the form of retail price increases.

The most important safety feature is actually part of your car's design, which is crashworthiness. This is something to consider when purchasing a new or used car.

Car size and structure

An obvious design characteristic influencing crashworthiness is size. The laws of physics dictate that, all else being equal, larger cars are safer than smaller cars. In relation to their numbers on the road, small cars have more than twice as many occupant deaths each year as large cars. Some people claim small cars are easier to maneuver in an emergency, so they're less likely to be in crashes. But small cars aren't less likely to be in crashes. Insurance claims for car damage, good indicators of overall crash involvement, are more frequent for small cars than large ones.

How the car structure performs in a crash is another important aspect of crashworthiness. Late model car designs include a strong occupant compartment, or "safety cage," along with front and rear crush zones designed to absorb crash energy in a controlled manner. Good structural designs confine crash damage to the crush zones in all but the worst impacts.

On-board warning systems
See Figures 1 and 2

• Brake system warning
• Windshield washer fluid level
• Coolant level
• Brake fluid level
• Door ajar
• Headlamp door position
• EGR or Check Engine
• High beam indicator
• Seatbelt light
• Cold engine warning
• Turn signals
• Charging system
• Transmission temperature
• ABS or Anti-lock Brake System
• SRS or Supplemental Restraint System
• Brake lining wear indicator light.

The high price of fuel created a demand for yet another light-- the fuel economy warning system. When the light comes on, it tells the driver he or she is pushing too hard on the gas pedal. High manifold vacuum equals good gas mileage and vice versa. The system simply reads manifold vacuum from a sensor, and when it drops to a predetermined level, a circuit is completed and the light is lit. This has become in many models what is known as the up-shift light. An arrow on the dash indicates the time to shift into the next gear to obtain optimum fuel economy.

If a warning light comes on, you must find out why. It means there is a problem either in the system being monitored or in the warning lamp circuit. Finding the actual fault is important and not very difficult. However, a wiring diagram may be needed to prevent confusion.

Looking at the typical warning light circuit, you'll see that the bulb is most often supplied with current through the ignition switch. Further examination reveals the most common way of completing the circuit and getting the bulb to light is by means of a sensor, which completes the ground connection. In this case, sensor is a fancy word for a switch that turns on or off according to specific conditions.

Consider a typical oil pressure warning light system. Current from the ignition switch flows through the warning lamp and from there to ground through the oil pressure switch. This particular switch is normally closed and the circuit is complete until the switch opens in response to oil pressure in the engine.

Just the opposite is true with the coolant temperature sensor. It is normally open and only completes the circuit when an internal element expands (in response to heat) to close the contacts. If the car has a cold engine warning lamp, the sensor includes two sets of contacts. One set is normally closed and opens as the internal element expands. This action breaks the ground circuit to the warning lamp. The other set of contacts functions if the temperature rises far enough to close them, turning on the high temperature warning.

If either of the temperature lights is lit while the engine seems normal, just unplugging the wires from the sensor will provide valuable diagnostic information. If the lights remain lit, there's a short to ground in the wiring from the lamp to the sensor. The service needed isn't to the cooling system, but to the warning system.

If the lights go out with the wires unplugged and the engine seems normal, it's entirely possible that the sensor has failed and needs to be replaced. Nevertheless, don't just unplug the wires and forget about them. This could be disastrous for the car owner should a cooling problem develop without warning.

Energy-absorbing bumpers
See Figures 3 through 5

Energy-absorbing bumpers in some form, capable of absorbing impact up to 5 mph, have been required by law on passenger cars since the early '70s.

On cars of the '70s and '80s it took the form of a piston, charged with an inert gas and a cylinder filled with hydraulic fluid. The cylinder tube is crimped around the piston tube. The crimping is backed by a grease ring to prevent the entrance of moisture and/or dirt. The piston tube is attached to the bumper and the cylinder tube is attached to the frame. Extension is limited by a stop ring.

Some oil wetting is normal due to seepage of the grease ring behind the crimp. Hydraulic fluid leakage in the form of noticeable dripping indicates a failed unit.

Some scuffing of the piston is normal in average use. Obvious damage to the unit, such as dents or torn mounts, indicates a failed unit. Repair is not possible. Defective units must be replaced.

The hydraulic or gas charged bumpers worked as follows: On impact, the bumper makes contact with the barrier. As the bumper is pushed back, hydraulic fluid is pushed past the tapered metering pin, absorbing the impact. As the bumper is stopped, hydraulic fluid in the front chamber has forced the floating piston foreword, compressing the gas to return the bumper. On recovery, compressed gas forces the fluid to return to its original chamber and the bumper is returned to its original position.

Cars of the 90's began took on more rounded shapes for increased aerodynamics and fuel efficiency. Many manufacturer's took this opportunity to reduce weight and cost by styling new crushable front bumpers made if lighter materials. These assemblies are normally made of an aluminum or steel crushable bumper covered with a plastic material (often painted to match the color of the body). In addition, the mounting units are designed to crush on impact. As an assembly, this offers the same or greater protection than the older hydraulic design. The added advantage comes with the reduced weight thus providing greater fuel economy to the vehicle.

In crashes, people need to be retained within the occupant compartment and not be ejected, as to reduce the likelihood of serious injury. Lap and shoulder belts play an important role in this. In effect, they retain you to the occupant compartment so you decelerate with it instead of slamming into hard interior surfaces. But not all belt designs are the same. Some are easier and more comfortable to use . This is important because a comfortable belt is more likely to be used every trip. Choose a car with belts that comfortably fit you and your family, and wear them.

All new passenger cars have shoulder belts on inertia reels that allow upper body movement during normal driving but lock during hard braking. Some cars have a second lock, too. You can test this by tugging sharply on a belt. If it locks, it's dual locking.

Some cars have tensioners that activate in more serious frontal crashes to reduce belt slack which, in turn, reduces the risk of head and chest impacts with hard interior surfaces.

Air bags
See Figures 6 through 9

Even the best belt designs can't prevent all head and chest impacts in serious frontal crashes. Air bags help by creating an energy-absorbing cushion between the upper body and steering wheel, instrument panel, or windshield. To get the maximum benefits, you should use a belt and sit away from the bag. This way, you'll be in position with sufficient space for the air bag to inflate rapidly and create a protective buffer.

Driver deaths in frontal crashes are about 20 percent lower with air bags than in similar cars without them. At the time of publication, it has been estimated that more than 2,500 lives have been saved. But in some circumstances, air bags can cause injuries, mostly minor, but occasionally serious or, in rare cases, fatal. The most serious injuries occur when people are very close to air bags when they first begin to inflate. Some of the deaths have been infants in rear-facing restraints and unrestrained or improperly restrained children. This risk can be eliminated by making sure all youngsters travel in the back seat.

Although different manufacturers' systems vary slightly, the air bag system is composed of a few basic parts. Two sensors located in the area of the front bumper, or in the firewall area, sense the impact. The sensors activate inflator(s) that blow-up a passenger air bag in the right-hand side of the dashboard, and a driver air bag located in the steering wheel hub.

The system has an indicator lamp activated by the ignition key to let you know the system is working. If the car is involved in a frontal crash equivalent to running into a stationary barrier at least 10-12 mph, the sudden deceleration (impact) causes the sensor to activate a gas cartridge that instantly inflates the air bag preventing the occupants from contacting the inside of the car. The air cushions absorb the impact.

The air bags themselves are porous and the air is actually beginning to escape as they are being inflated. The entire process (sensing, inflation and partial deflation) is completed in about 125th of a second, or about the time it takes to blink your eye.

Seating position

Sitting very close to the steering wheel increases your risk of hitting it in a crash, even if you're using a lap and shoulder belt, and it doesn't allow sufficient space for the air bag. So it's important to position yourself away from the wheel. Choose a car that allows you to comfortably reach the pedals without being close to the wheel. Shorter people who cannot reach pedals without getting too close might consider cars equipped with a telescoping adjustment to move the steering wheel away from your chest. And remember that sitting very close to an air bag increases injury risk from the bag itself. This is another reason to position yourself away from the steering wheel.

In side impacts, some of the more serious injuries occur when the force of a crash drives a door into an occupant. All 1997 and later model passenger cars must meet federal side impact crash test requirements intended to address this problem. Vans, pickups, and utility cars were not required to meet this standard until the 1999 model year, though many did prior to the deadline. Manufacturers typically have used extra padding to meet this standard, but some also are installing side air bags to protect drivers and right front passengers. Side air bags were fist introduced in some 1997 models including the Audi A8, BMW 5 - and 7 - series, Cadillac Catera and DeVille, Lexus LS 400, Mercedes E,S,SL classes, and all Volvos.

To prevent people's heads from being snapped back, causing neck injuries in rear-end crashes, head restraints are required in the front seats of all new passenger cars. Rear-seat head restraints aren't required but are found in more and more cars.

All head restraints aren't the same. Some are adjustable, and some are fixed. Head restraints also vary a lot in height and how far they're set back from occupants' head. To prevent neck injuries, it's necessary for head restraints to be directly behind and close to the backs of occupants' heads. Make sure the ones in a car you're considering can be positioned this way. In general, fixed head restraints are preferred because they don't have to be adjusted for different occupants. If the ones in a car you're considering are adjustable, check that they can be positioned behind and close to the back of your head. Make sure they lock when adjusted, because some don't.

Don't be surprised if a head restraint cannot be positioned for adequate protection. Among more than 200 1997 model passenger cars in which the NHTSA measured the head restraints, more than half had poor geometry. Only five cars had good head restraint geometry. They were the Honda Civic del Sol, Mercedes E class with restraints that adjust automatically, the Toyota Supra, and two Volvo models-- the 850 and 960.

An infant who can't sit up should be placed in a rear-facing restraint secured by an adult safety belt in a car's back seat. Such restraints provide very good protection but can pose a safety risk if placed in the front seat with a passenger air bag. An inflating bag could hit the restraint with enough force to cause serious injury or death. In cars with no rear seat, automakers may install manual cut-off switches for passenger air bags. Drivers of these cars should check the passenger bag status before every trip.

Don't position an infant in front if there's a passenger air bag!

When infants first outgrow their safety seats and can sit up by themselves, they should travel in special child restraints -- again, held in place by adult safety belts in the back seat. When used properly, such restraints provide good crash protection, and they're offered as optional built-ins in the back seats of a number of passenger cars. Older children can use either adult safety belts or booster seats to make the adult belts fit better. What's crucial to remember is that infants and children should ride, properly buckled into special restraints or safety belts, in the back seat. This was true before air bags, and it's doubly true now because riding in back puts children out of the paths of inflating air bags. If children must ride up front, set the seat all the way back. Don't let a child fiddle with radio dials, for example, because this can put the youngster's head too close to the air bag.

Continue with Part 2 of Safety systems and safety check

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