LOS ANGELES -- California, anticipating a flood of older drivers on increasingly crowded roads, has taken the first steps toward an expected transformation of the nation's automobile-traffic system as the baby boom generation reaches retirement age.

Officials of the state Department of Motor Vehicles (DMV) have begun planning for new night and peripheral-vision tests, video simulation exercises and longer and more complex written examinations in what would be the first significant change of the state's licensing system in a half-century.

The California effort, national safety experts said, is only the beginning of a series of engineering and legal changes being discussed in several states to prepare for 30 years from now, when 50 million Americans 65 and older will be eligible to drive. Half of them will be at least 75.

The safety experts said they expect much larger and better-lighted letters on roadway signs, more left-turn lanes and signals, pedestrian-crossing signals set for slower walking speeds and much more sophisticated driver's license tests. These would be designed to give limited driving privileges to some older Americans, who would otherwise be deprived of mobility, and to keep dangerous drivers off the road.

"California is at the forefront," said James L. Malfetti, a retired Columbia University professor who has helped to lead the movement to accommodate an aging population. "The technology is also rapidly catching up to the wish to have these new measures."

Ray Peck, chief of research and development for California's DMV, said the suggested changes are designed to assure competence of all drivers, not just the elderly. But he acknowledged that some of the new devices, such as ophthalmological equipment to test the natural deterioration of night and peripheral vision, would have more impact on older drivers.

George Gaberlavage, a senior analyst with the American Association of Retired Persons, said his organization is monitoring the proposed changes for signs of illegal age discrimination. He endorsed a recent research report emphasizing the need to help older Americans stay behind the wheel.

"Mobility is essential to the quality of life of older people," said the 1988 Transportation Research Board report written by Malfetti and others, "and all trends indicate that the majority of the transportation needs of older citizens into the next century will be met by the private automobile."

Some densely populated areas can provide buses and other alternatives to private vehicles, but the vast majority of Americans will retire in suburban and rural areas where "the cost to society of providing alternative means of mobility would be enormous," the report said.

California's DMV sponsored a conference in San Diego two months ago to discuss ways to forestall a crisis created by growing numbers of drivers, particularly recent immigrants and the elderly, trying to navigate more crowded, inadequately designed roads.

The Transportation Research Board noted that design standards for highway-sign letter height and other important items were set in the 1940s and based on a driving population only 7 percent of which was 65 or older. That proportion now is 12 percent and expected to grow to 17 percent by 2020.

Stephen Godwin, a services program officer with the board, said "licensing issues are at the forefront now in the policy debate" about handling older drivers.

Safety experts cautioned that in an age of improved geriatric medicine, nutrition and exercise, many 75-year-olds perform as well behind the wheel as their children. But in most drivers, visual acuity declines with the hardening and clouding of the crystalline lens in the eye, and this process, combined with reduced pupil size, hampers night vision.

"It's like every 13 years somebody puts another pair of sunglasses on you and drops another filter in front of your eyes," said Hal Lunenfeld, an engineering psychologist with the Federal Highway Administration. He said several automobile companies are working on devices to help older drivers, including an infrared system being tested at General Motors.

Bill Gengler, a DMV spokesman, said new vision tests and video simulations -- essentially calibrated video games -- would assure better mobility and safety for all drivers. The department also could tailor special license restrictions to give impaired drivers now denied licenses a chance to drive in daylight or take short trips to church or the local mall.

Patricia Waller, head of a highway-safety group at the University of Michigan, said many states are interested in improving equipment and techniques but cannot afford larger, better trained staff to make the new methods work.

Even after tests are complete, California's plans would require legislative approval. The state's licensing requirements are relatively loose, with some drivers allowed to go as long as 12 years without being retested.

Lawrence Greenberg, chief of motor vehicle services in the District of Columbia, said he had worked for improvements in the system while serving as chairman of the drivers license committee of the American Association of Motor Vehicle Administrators. The District is one of few U.S. jurisdictions to require a written and road test of all drivers who turn 75.

Jeanne Chenault, spokeswoman for the Virginia Department of Motor Vehicles, said her department put special restrictions on 1,040 drivers last year because of problems reported by family, friends, physicians or police.

Howard McClanathan, director of licensing and school vehicle safety for the Maryland Motor Vehicle Administration, said his office also encourages such reports and requires that each driver be given a written and vision test every four years.