On Wednesday, the Diamond Cab Co. got its first call this month requesting the discount taxi service it offers in Arlington to and from three Metro subway stops during rush hours.

The service, remarked Harold Oakes, who is supervising it for Diamond, is "pretty much of a flop."

Other taxi industry officials agree.

The shared taxi shuttle service, begun in January by Diamond and in February by Red Top Cab Co., provides trips at less than half the cost of regular metered service to many Arlington destinations. Under the county-sponsored program, the cabs pick up commuters at their homes and cruise past or wait for commuters at the Rosslyn, Crystal City and Pentagon City Metro stops from 6:30 to 9:30 a.m. and 3:30 to 6:30 p.m.

When a cab picks up a passenger at any of the stations it is permitted to wait 10 minutes for another passenger going to the same vicinity. If none appears, the original passenger gets private service for the discount price. Cab officials say they need three passengers for each trip to make a profit.

But the passengers were "few and far between," according to Ritchie Gaylen, executive vice president of Red Top. Although the company spent more than $10,000 to promote the service, the largest number of requests for one day was 15, he said. That record was in the first couple of months, but the calls have "dwindled to almost zero," he said.

"It really was a pretty good idea, but people just aren't share ride oriented as far as cabs go," said Oakes of Diamond Cab. He said Diamond has spent about $3,000 on promotion of the program.

Gaylen said he believes the program could work if the fares were subsidized by local government so they could be kept lower and if the company could spend more on promotion. But he did not blame the Arlington County Board, saying they're wrestling with Metro all the time and who wants another cancer."

Oakes suggested that bus routes are so convenient in Arlington that people may have no need for the taxi service. He said Diamond will try another promotional campaign in the fall to increase ridership.

Under the program the county is divided into seven zones and fares are calculated according to the zones in which the trip originated and ended. A trip that does not cross a zone boundary costs 90 cents, while one crossing one boundary is $1.25 and two boundaries is $1.90.

Northern Virginia cab rates are normally metered and fares depend on the distance of the ride. The present rate is $1.20 for the first mile and 10 cents for each seventh of a mile after, officials said.