THE FOLLOWING CONVERSATION is reported from Metro's crowded 6-K bus, rolling along yesterday morning from Alexandria to George Mason University in Fairfax. A young man said to a young woman: "Do you take the bus all the time?" Reply: "I guess I'll be taking it from now on. I can't afford to drive anymore."

The Carter oil-conservation policy is working. That policy depends partly on public cooperation, but mostly on rising prices. The young woman on the 6-K probably considers it inconvenient and irritating. But is its not nearly so irritating and inconvenient as sitting in a gasoline line. Nor is it so damaging to her future prosperity as continuing to pour out $98 billion a year -- the present rate -- for this country's oil imports. Nor is it so dangerous to her security, or the nation's, as the past American practice of leaning heavily on fragile governments in the Persian Gulf to keep pumping out more oil than their own economists and technicians considered wise.

Mr. Carter's oil policy, as many people have noted, conflicts with his inflation policy. The first pushes prices up by decontrolling oil, while the second tries to hold them down. At his press conference, the president was asked about that. His answer was precise and useful. There are only two ways to cut American dependence on foreign oil, he said. One is to raise American production of all kinds of energy, and the other is to cut needless use and misuse of it. Holding down prices with controls undercuts both of those goals. Cheap oil, for example, has been the main reason for the very slow progress in developing solar energy.

Raising oil prices certainly contributes to inflation. But reducing American oil imports is now far more urgent than restraining prices. It's not even a choice because, as the past decade's experience demonstrated, oil price controls actually accelerate the inflation. By holding down prices, the controls contributed to the enormous surge in U.S. demand for oil -- and that surge was responsibile for doubling the price last year. Americans are going to have to get oil comsumption down sharply before they can hope to stabilize prices.

For nine years, since oil prices were first imposed in 1971, Americans under three presidents and five Congresses have tried to do it backward. The result has been a cumulative disaster. Prices are wildly high. Inflation is at record levels. And the Persian Gulf region, awash with its new wealth, is less stable and more threatened than at any time since the collapse of the Ottoman Empire.

The young woman on the 6-K did not seem particularly pleased to be there. The bus has lately been getting a bit too crowded for comfort. But American consumption of oil is running well below last year's level. It is no longer accurate to say that the United States has no effective energy policy. The woman on the 6-K not only benefited herself by leaving her car at home, but did the country an important service.