Washingtonians should recognize a basic fact about public transportation--namely, that Metro can move the most people at the lowest true cost to all jurisdictions if bus service and subway service are free.

Free? Yes, free, ladies and gentlemen. If you will think the matter through, I believe you will see that the idea is not so radical as it sounds.

First, as municipal officials, the Metro board members should consider not only operating costs, but the true full cost of transportation to the taxpayers they represent. The District, Maryland and Virginia are all currently paying the costs of freeway maintenance, of local street and highway departments, of traffic patrols at peak commuter hours, of special police for traffic control, of additional bridges and approaches, and of the garaging of all the cars.

For example, the new Bureau of Printing and Engraving includes space for 2,000 cars --a very costly use of downtown floor space. Further example: the current annual cost to the District alone for maintenance of streets is about $8.3 million. Adding the costs to all jurisdictions, the metropolitan area must spend about $70 million on streets costs.

In addition to those costs that are paid for by taxes, each commuter who comes to work by car pays out-of-pocket the cost of that ride. And we are all paying for unhealthy air with asthma, sinus and lung conditions and lead poisoning.

These are the costs of our current way of moving most people: the private car. But just think about the benefits to all commercial areas, city and suburbs, if we cut down the number of cars. Unchoked streets would permit better commercial deliveries. Tourists would have better access to historic sites. No one would have to sleep in a car to get a parking space. Noise levels near all major streets would be back to humane levels. People could walk uninhibited. Rational land use and planning would be possible because municipalities and businesses would know where most people were coming and going by bus or subway.

I believe we are face-to-face with disaster in our city and in surrounding commercial areas. Someday soon, a car will come off the assembly line, be driven down the street, and stop--with no place to go because everything will stop. With each of us doing our own thing, driving our cars, we are on a self-destruct path.

Besides, we already have invested enough in public mass transit to deserve a free ride. We have invested the cost of buses and are paying $5.2 billion for the construction of the Metro rail system, the most expensive public works project in America. The operating expenses are a tiny percentage of that cost.

Free service would dramatically increase the number of riders on subways and buses, especially if combined with:

* improved bus service to areas where most people live;

* good bus service to subways; and

* higher parking fees in the city.

If a rush-hour roundtrip from Rockville cost $3.50 by car and $3.50 by bus/subway, a commuter will use the car for convenience. But if the difference is between $3.50 and nothing--no cost at all--I believe the commuter will ride the bus/subway.

Increased ridership on public transportation would reduce all of the current true costs that people are now paying for transportation. It would reverse the 20-year drift of public habits away from public transportation. Lack of interest in public transportation has permitted poor service. The simple fact of free transportation would make available service to groups that are now hard put to get around: the teen-ager without a family car; the elderly; those who cannot afford to maintain a car and therefore have trouble getting to jobs; and those who must maintain a second car in the absence of good transit service.

Where would the money come from for operating expenses? First of all, money would come from the savings in true transportation costs just outlined. Funds should come from the Highway Trust Fund. But if that proves politically impossible, why not a retail tax for public transportation? One-half of the 1 percent sales tax in the three counties supporting the San Francisco Bay Area Rapid Transit System would pay all of its operating expenses annually. The sales tax is a regressive tax, but in this instance a service would be provided for the tax.

We are familiar with the cycle of public transportation everywhere: high fares, low ridership, higher costs per rider, and therefore higher fares, even lower ridership, and so on--to the point where people can't afford to ride public transportation, and public transportation is bankrupt. With free rides, you would have riders. Further, you would have a stable financial tax basis for public transportation.

In San Francisco, the BART staff supports a free plan, and the state legislature is seriously studying the possibility. Back here, with free Metro service, people immediately would save yet another cost: the cost of that complicated fare collection system, including its design staff and the employees who do the collecting. We would save the work time required for special school fares, tickets for the elderly and any other different rates.

I hope that this Metro board will distinguish itself by considering and adopting a no-fare public transportation system. The financial and public interests of all its constituents and the region would be the better for it.