Before travelers pack their bags for the long holiday weekend and open their wallets to take advantage of the "special" at the local rent-a-car agency, they might want to check the facts and figures.

One fact, according to the Consumer Affairs Committee of the Americans for Democratic Action, is that a Fourth of July special might not be a great deal. That special actually may cost more than any other weekend special, the committee reported.

The committee's survey of 27 national chains and independent car rental companies in the metropolitan area found that some advertised specials charge customers the same as regular weekend rates or more. Most of the agencies surveyed also did not inform customers that purchasing collision insurance was optional, the committee said.

"Consumers should be wary of the word 'special' which is much abused. 'Special' has become a word of advertising rather than a word of truth," said Ann Brown, chairwoman of the committee, which released the survey's results yesterday.

Of 17 companies that advertised specials, "only seven were real sales," Brown said. "Eight of the firms charged the same or more and in two of the firms, customers only saved 5 cents, not even enough for a cup of coffee."

Brown said that according to the National Insurance Consumer Organization, approximately 60 percent of car owners carry collision insurance that applies when renting an automobile. Yet only four of the 27 firms surveyed indicated the insurance was optional and that the renter's own insurance might cover it.

Jane Moss, representative of the American Car Rental Association, said the committee's report was "very inaccurate and misleading. Instead of helping to enlighten the consumer, it's just made things more confusing."

Moss said that rental rates depend on several variables, including size of car, days of the week rented and length of time used. "I don't know how it was conducted and under what circumstances," she said, adding that she does not think misleading advertising by car renters is as widespread and rampant throughout the industry as the committee said.

She also said that the collision insurance option is clearly stated on contracts, and that the survey indicated that most rental car company representatives said so when called.

"It's not something that some fast-talking counter rep says, 'You have to sign it one way or another, whether you want it or not,' " said Moss.

The committee plans to refer its findings to the District Consumer Protection Office for review.