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Driving beyond 65.


Senior-citizen drivers are spurring Detroit to develop safety features that can reduce glare, avoid collisions, and automatically handle cumbersome chores such as removing windshield ice and checking tire pressure.

Licensed drivers over 65 represent the fastest-growing segment of the automotive population. By 1995, according to the National Highway Traffic Safety Administration (NHTSA) in Washington, D.C., 13.5 percent of licensed drivers will be 65 or older.

Though senior citizens are among the most experienced drivers on the road, they are subject to slower reaction times and reduced eyesight than younger motorists. As a result, engineers and automotive designers are developing a host of new features that will provide enhanced safety and convenience for older drivers-as well as for the rest of the driving public. These include head-up displays, image-intensification and night-vision technology, reduced glare headlights, collision-avoidance systems, crash restraints such as air bags, heated windshields, and tire-pressure sensors.

In-Car Displays

For the older driver, more legible in-car displays and controls can play a major role in improving safety and increasing driving pleasure. Research by Douglas Poynter at the General Motors Research Laboratories (Warren, Mich.) has shown that older people need at least contrast required by younger people to pick out a letter or image from its background. Related studies have shown that yellow, orange, and white displays on contrasting backgrounds are the easiest to read. Research has also indicated that, for maximum legibility, letter heights of 5.5 to 6.4 millimeters should be used for important instruments such as speedometers.

The fact that older drivers need more time to process and react to complex visual information has several important implications in instrumentation design. The first is that analog displays are preferable to digital ones. According to Poynter, analog symbols are easier to interpret than the numerals that are used on digital displays. Drivers can read analog gages with a quick glance, without refocusing their eyes. However, digital gages require refocusing and time to interpret the data. In addition, most analog symbols can be picked up deeper in a driver's peripheral field of view than can digital symbols.

Another problem involves the time it takes to adjust from viewing distant objects outside the car to looking at nearby displays in the auto's interior. One solution is the head-up display (HUD), an idea borrowed from military aircraft. HUDs are available as an option on a number of cars, including the 1990 Pontiac Turbo Grand Prix. The HUD projects information from key instruments such as the speedometer, fuel gage, and warning lights, onto the windshield within the driver's field of view. This allows the driver to check the instruments without taking his or her eyes off the road.

Driver viewing adjustment problems can also be minimized by large, simple controls in familiar locations with familiar shapes that work logically.

In the future, the virtual image display (VID) may offer an improvement of HUD designs. The VID uses special optics with either a digital or analog display so that the image appears as if it were located several feet outside the vehicle. Drivers can easily read a VID display without taking their eyes off the road. Night Driving

Because older drivers need considerably more light to see an object and have less contrast sensitivity, night driving can be potentially dangerous for them. Dark objects against a dark background are especially troublesome.

Image-intensification and night vision technology provide clearer pictures in the dark. Image-intensification equipment electronically magnifies the faintest reflection from objects-even in moonlight-so they can be easily seen. Night-vision goggles are already routinely used by helicopter pilots on night missions and by military vehicle drivers who need to drive without headlights. One disadvantage of the current generation of equipment is their narrow field of view, which gives the user very little peripheral vision.

Thermal imaging, a related technology, may one day help drivers see through rain, fog, and snow, as well as at night. Every object gives off thermal or infrared radiation that can be used to generate an image. This picture can be displayed on a video screen on the instrument panel or on the windshield using a HUD. Thermal imaging is currently used on a number of military aircraft in the form of the infrared radiation detection system (IRDS). The systems are expensive, however, and their use in automobiles may be a ways off.

Glare is another problem that grows worse with age, since scattering of incoming light within the eyeball is greatly increased and glare tolerance decreases. Oncoming head-lights are the main source of the glare problem. One solution comes in the form of headlights that operate in the ultraviolet region of the spectrum; they are currently being developed by the Swedish automaker Volvo.

The problem of reflected glare has also been attacked with the electrochromatic rearview mirror, which is already available on some cars. Unlike existing day/night mirrors that darken everything equally when used on the "night" setting, the electrochromatic mirror automatically adjusts the amount of light it reflects to compensate for different glare situations. It also automatically returns to the normal mode when the glare source is gone.

An electrochromatic mirror contains two photocells. One cell faces forward and detects darkness, while a rear-facing cell detects the glare generated by headlights located behind the car. The typical electrochromatic mirror has two reflectance levels: 20 to 30 percent for urban use where glare is less severe and 6 percent for rural use where glare is more of a problem. By comparison, the reflectance of a standard day/night mirror is 4 percent on the night

Collision Avoidance

Collision avoidance offers another route to improved safety. To date, the most significant advances in collision avoidance have been made in antilock braking systems (ABS). An ABS is designed to keep a car's wheels rotating as the brakes are applied to allow a controlled stop without locking the brakes and losing steering. An ABS-equipped car almost always stops within a shorter distance than a car outfitted with conventional brakes. Drivers are also better able to steer an ABS-equipped car to avoid obstacles. ABS is now available as an option on many cars. It is likely that in a few years it will become a standard item on most models.

Another collision-avoidance device is the Clearance Sonar obstacle warning system from the Japanese automaker Toyota. Here, transmitter-receivers are mounted in the bumpers at the four corners of the car. When the car comes within about 20 inches of an obstruction, the driver is warned by a flashing light and buzzer. A more powerful variation on this concept that is currently being developed by G.M., the Near Obstacle Detection System, would detect other vehicles up to 15 feet away and therefore would be useful in lane-changing situations. If the turn signal is activated and another vehicle is within the 15-foot range, the driver would be given a warning signal. In the future, advanced collision-detection units could be designed around radar, TV cameras, or laser range finders.

Navigation systems, which often use small computer and cassette-based maps, help guide drivers to their destinations across unfamiliar territory. (See October, page 12, for a discussion of auto map systems.) However, according to Anthony J. Yanik, a leading expert on older-driver safety and a member of G.M.'s Environmental Activities staff, in-vehicle navigation systems would be of limited value to older drivers because these motorists tend to stick to familiar routes. In addition, viewing a CRT requires taking one's eyes off the road. This may cause problems for older drivers who must concentrate more on traffic to compensate for their longer reaction times. However, navigation devices tied in with congestion reporting systems that send traffic flow data back to a central computer could be used to help steer drivers around congestion and avoid gridlock.

Monitoring roadway congestion is a key objective of intelligent vehicle/ highway systems (IVHS), which is another collision-avoidance technology that is being applied to the benefit of senior-citizen drivers. (See October, pages 72-75, for a discussion on intelligent highways.) IVHS designs often combine collision-warning, automatic speed control, and-in the future-completely automatic guidance systems. IVHS programs are currently underway at the Illinois Department of Transportation, Fiat, BMW, and G.M.

Crash Protection

Advances in crashworthiness are also having an impact on improved safety for older drivers. Devices providing improved crash protection include passive restraints such as air bags and automatic scat belts.

Improvements in side-impact protection are especially important to older drivers. Research shows that drivers over 50 are about three times more likely to be involved in a multivehicle side-impact crash than a single-vehicle accident. New federal regulations will force automakers to design stronger doors for better side-impact protection. In addition, Yanik said, softer energy-absorbing materials on doors will provide added

The Little Things

A number of devices that appear to be time-saving gadgets can actually help make cars safer for mature motorists. For example, the electrically heated windshield eliminates the physically demanding chore of scraping off ice during cold weather. The electrically heated windshield can melt a thick layer of ice in about 3 minutes. In comparison, a standard defroster takes at least 15 minutes to clear a window sufficiently for safe driving. Heated outside rearview mirrors are another aid to visibility.

Checking tire pressure can sometimes be an inconvenient chore. Yet underinflated tires are not only a safety hazard, but can lead to faster tire wear and poorer fuel economy. Tire-pressure-sensing systems can be a great help. Sensors in each tire continually measure tire pressure and light a warning light on the instrument panel when the pressure becomes too low.

A number of sensor systems are becoming available. The low-tire-pressure warning system (LTPWS) made by Epic Technologies Inc. (Norwalk, Conn.) is currently available on Chevrolet Corvettes. The LTPWS consists of pressure sensor assemblies located in each wheel and receiver and indicator units mounted inside the car. The sensor has a temperature-compensated pressure switch that opens when the pressure inside the tire drops below a preset value. The switch has an accuracy of

I psi and is sealed against moisture. The German automaker BMW is offering a similar unit on its model 850i super coupe sold in the United States.

Improving safety for older drivers also requires a comprehensive approach, according to the NHTSA. The agency has developed a "Traffic Safety Plan for Older Drivers," which noted the important contributions vehicle designers can make to crash avoidance and improved vehicle crashworthiness. The plan also emphasized that road safety can be increased through better highway design, optimum road lighting, and easier-to-read roadway signs and markings. The third facet of NHTSA's program covered behavioral scientists, who can help make roads safer by developing improved driver education methods and programs.
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Title Annotation:safety systems for senior citizens who drive
Author:Siuru, Bill
Publication:Mechanical Engineering-CIME
Date:Dec 1, 1990
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