A new kind of public carpool system began last week in the heavily traveled commuter corridor between Dale City and Washington.

While more than 100 enthusiastic Woodbridge-Dale City residents have signed up, only a few dozen have actually taken part in the experiment so far.

The carpooling, which is being sponsored by the Metropolitan Washington Council of Governments (COG) and Prince William County, allows commuters to hop in any of dozens of car pools leaving at different times, but going to and from the same place: from Dale City's fringe parking lot to the Pentagon Metro station.

Dubbed CARTS (Community Auto Rapid Transit System), the system has been tried only in Denver and San Francisco and failed in both cities, according to COG officials.

But in Washington, the officials say, the experiment has at least two things going for it that it did not have in those western cities. First, each rider pays the carpool driver 75 cents to go to the Pentagon Metro station, which cuts some of the driving costs and gives drivers a financial incentive. Secondly, if the car has four people in it, it can use Shirley Highway bus lanes, which saves as much as 30 minutes on the 25-mile trip from Dale City to Washington.

One of the first persons to sign up for CARTS in Washington was Air Force Maj. Alan Aber, who ferried full carloads the first two days last week. Even on a day when he had to leave for work before 5:30 a.m., too early for most fellow commuters, he stopped by the Pentagon bus loading island in the afternoon to see how the CARTS program was going.

"I sure hope it succeeds," Aber said. "It means using less fuel and it's faster. And I don't feel quite as guilty driving in by car."

Aber, who has been carpooling privately for several months and paying $10 a month for a parking space in a Pentagon lot, says he tried using the Colonial Transit commuter buses that run daily between Washington, Dale City and other suburban Virginia locations. He stopped riding the bus, he said, because there were so many breakdowns on the line.

James Harte, a Department of Defense transportation specialist and a member of the Prince William County mass transit committee that helped launch CARTS, also is a former bus rider and private carpooler who was glad to see the CARTS program launched.

"Colonial Transit had some problems and cost $15-16 a week to the Pentagon . . . and if you've ever been in a (private) car pool you know its problems. You've got to drive on a certain day, be in a certain place at a certain time and, if you oversleep or something, you're stuck," said Harte.

The main advantage of CARTS, said Harte, is that "there are whole bunches of car pools, any one of which you can take."

So far, however, CARTS has had few bunches.

"We knew it would be a bad time of year to start," said COG's senior transportation planner William Mann. "The weather's been bad. It's dark. It's near Christmas and people are taking leave and vacations, and we need more publicity. But if there's a gas crisis, this is something you can count on and can be started up overnight. It doesn't take three weeks to gear up and organize."

One day last week, from 4:30 p.m. to 6 p.m., Mann and another COG planner stood on a traffic island just south of the Pentagon's Metrobus loading zone, wearing signs saying CARTS and waiting for carpoolers. Three Dale City cars came up with CARTS signs in their windows. Two left without passengers and one, driven by Harte, left with three, enough to get in the Shirley Highway bus lanes.

"It's discouraging so far, but if the more than 100 people who signed up showed up, we could get it going and it would run itself," Mann said. COG hopes that, if CARTS succeeds, it will become a private carpool club run by commuters.

The CARTS cars are only going to the Pentagon Metro station so far, and Mann said many of those who signed up want car pools that go directly downtown.

"We hope to expand to Farragut Square among other places," said James McCoart, a member of the Prince William Board of Supervisors and one of the chief supporters of CARTS. "We just need a sufficient number of drivers and riders each day to make it succeed."

COG expects to continue its support of the project as least through this week, signing up drivers and passengers who show up between 6 a.m. and 7:30 a.m. at the Dale City fringe parking lot, where Colonial Transit buses also leave, and between 4:30 p.m. and 6 p.m. just south of Metro's Pentagon bus loading islands.

A spokesman for Colonial Transit said the company had a 50 percent drop in passengers after last winter's "bad weather caused us a lot of breakdowns. But we've acquired some later-model buses and made great improvements in our preventive maintenance."

Colonial Transit, a private bus company, has more than 50 routes in suburban Virginia and runs 16 buses a day from Dale City to the Pentagon and different points in downtown Washington. Commuting via Colonial costs $18.05 to Washington and $15.60 to the Pentagon a week, and $5.10 to Washington for a one-day round trip.