Since The Post has used considerable ink to address the horror stories involving taxicab overcharges in this city, readers might be interested to know that with a little attention to detail and a bit of patience, taxi passengers can find a friend at city hall.

A recent taxi trip from 19th & K streets NW to National Airport wound up costing me $12.80. Although I knew that fare was too much, I was late for my plane and paid it after a brief argument -- taking care to note the cab's license number.

Through the D.C. switchboard, I found Moe Harmon, a rate supervisor at the Washington Metropolitan Area Transit Commission. He told me to put my complaint in writing, using as much detail as I could -- in this case, the license number, the name of the cab company, a sketchy description of the driver and the date and time.

I had forgotten the incident when, three weeks later, a return letter arrived from Harmon. In it, he explained the metropolitan taxicab rate system in detail, told me what the fare should have been (about $7.30) and reported that the offending driver had been located and "sternly counseled." Accompanying the letter was a money order for $12.80 -- a refund from the driver for the whole fare charged.

Okay, so it's just one little good news story. But just when you thought the whole D.C. government was about to drown in its own incompetence, it's refreshing to read and re-read Moe Harmon's letter, especially the last sentence.

Thomas G. Goodwin This responds to your letter of Aug. 17, concerning taxicabs rates between 19th & K Street NW and Washington National Airport.

In a District of Columbia taxicab, the rates are:

$1.80 for the first mile;

$ .50 for each additional half-mile or fraction;

$1.00 for each extra passenger in a pre-formed party; and

$1.00 surcharge 4 p.m. to 6:30 p.m. for trips originating in D.C., Mon.-Fri., except holidays.

Trips originating at National Airport are also subject to the FAA 50-cent airport gate fee. For details on these and other rates for baggage, waiting time, personal service, phoning for a cab, etc., please see the enclosed Order No. 2719 implementing the current interstate rates for D.C. taxicabs. Also enclosed is a copy of our Order No. 91 containing taxicabs regulations which may be of interest.

Here's how it works. The first person or pre-formed party to enter a cab has control of the vehicle, and others may not be transported without the first party's permission. In a D.C. cab the driver should record his odometer reading at the origin point and transport his passenger(s) to their destination(s) via a direct route. At the final destination he records his odometer reading again, determines the distance traveled and applies the rate to determine the correct fare.

For example, we estimate the distance between 19th and K Street and Washington National Airport to be chargeable at 5 1/2 miles, or $6.30. This could be affected by direction of travel, the airline terminal of origin or destination, temporary street closings or turn restrictions, etc.

It is also possible to get a metered cab from one of the suburban jurisdictions at National Airport. In this circumstance, the driver is required to use his meter for interstate trips, as well as local trips. Meter rates differ from jurisdiction to jurisdiction, presently ranging from $1.80 to $2.20 for the first mile, and from $1.00 to $1.20 for each mile thereafter. Meters, however, also run on time as well as mileage, so a slow trip in heavy traffic may cost more. Too, meters generally register fares in increments of 20 cents per 1/6 of a mile, rather then halves, so you get a more finite count. Luggage charges in metered cabs also vary among jurisdictions. Applicable rates should be posted in each cab.

Yes, it is complex, owing to the fact that a half-dozen local jurisdictions license and set rates for their own taxicabs. However, any complaint relating to a fare for interstate taxicab service in the Metropolitan District will be processed by this office.

Perhaps the most important thing to remember about complaints is that they should be filed in writing as quickly as possible and should include some dependable means by which we can identify the driver or vehicle -- for example, the license plate number and jurisdiction -- or the cab company name and cab number.

There are 14,000 to 15,000 taxicab drivers licensed locally, and the vast majority are honest and responsible. Taxicab drivers are obliged to provide receipts upon request, but it is our experience that a driver who has just overcharged a passenger is likely to be inaccurate about identifying himself, so it is important that a passenger independently confirm or secure identifying data. We suggest that the passenger request a receipt at the beginning of the trip "indicating the correct mileage."

Concerning your specific complaint, the correct charge for this approximate 5 1/2-mile trip is $7.30, calculated as follows: Airport gate fee$0.00First mile$1.809 1/2 miles @ 50

each 4.50One additional passenger$1.00TOTAL $7.30

After discussing the case with the driver and with such a flagrant violation, he decided to refund your entire fare ($12.80). The driver has been sternly counseled with reference to the proper computation of interstate rates, his conduct and the proper display of his I.D. card.

I hope this information proves useful. An oversimplification of the situation would have been neater, but would not serve you or your colleagues very well. Please keep our number and address handy; we're here to help.

Moe Harmon Rate Supervisor Washington Metropolitan Area Transit Commission Suite 316, 1625 I Street NW Washington, DC 20006-3051 (202) 331-1671