On any given day, more than half of the 7 million elderly Americans who don't drive stay home because they lack adequate transportation alternatives, according to a report to be released today.

The report by the nonprofit Surface Transportation Policy Project was based on 2001 data collected by the U.S. Department of Transportation and was financed by AARP.

In Florida, 19 percent of the population 65 or older -- nearly 540,000 people -- reported themselves as non-drivers. In Palm Beach County, the only metropolitan statistical area surveyed, 15 percent of the elderly population -- nearly 40,000 people -- said they did not drive.

Elderly non-drivers are likely to be isolated and more prone to bouts of depression, alcoholism and physical ailments than elderly drivers, Dr. Byron Thames, an Orlando family physician and AARP board member, said in a conference call with reporters.

Compared with drivers, elderly non-drivers make 15 percent fewer doctor visits, 59 percent fewer trips for shopping and dining and 65 percent fewer trips for social, family and religious activities, the report said.

The report found that elderly non-drivers stay at home because public transportation is not available, particularly in rural areas and small towns. In some areas, specialized transit is available to elderly people with disabilities, but they must live near a public transportation route.

To demonstrate what public transportation exists in Palm Beach County, Palm Tran and Tri-Rail are sponsoring an outing today to Las Olas Boulevard in Fort Lauderdale. Today's outing is already booked up, but officials said other demonstrations are held whenever enough people contact the transportation agencies.

Anne Canby, president of the Surface Transportation Policy Project, said the report's findings highlight the need for greater support for public transportation and other transit alternatives aimed at older people, and on road improvements that include bicycle lanes and sidewalks to promote cycling and walking.

The House and Senate have each passed versions of a six-year transportation bill that would authorize an increase in federal spending for alternative transportation above the $456 million approved in 1998.