PEOPLE ARE DRIVING less than they did a year ago. But the refineries that normally build up their stocks after Labor Day have been producing less. One reason there have been no lines at filling stations is that the country has been drawing down its reserves.

The Carter administration is about to announce voluntary targets for gasoline conservation, state by state. That follows the president's appeal to the governors, in mid-November, for the "sharpest possible reduction" in energy consumption as a response to the cutoff of Iranian oil. But the governors did not seem enthusiastic at the time, and the campaigns for voluntary conservation have had only limited success.

There is a better way to avoid gasoline lines and that is to decontrol the price of gasoline immediately. Those controls will expire in 1981, in any case, along with the controls on crude oil. There is no public benefit in using the law to hold down gasoline prices for two more years.

The present moment is an ideal one for decontrol. It is a season of the year when consumption is relatively low, and will remain low for four or five months. The eruption in Iran has drawn people's attention to the urgent need to be very careful with oil, even to the point of applying so unwelcome a sanction as higher prices.

In the best of all worlds, decontrol of gasoline would be accompanied by a stiff tax to return part of that higher price to the public that pays it. In reality, that is not possible. The inordinate difficulties encountered in he Senate by Mr. Carter's windfall tax on crude oil suggest that the prospects for a gasoline tax are at best dim. The real choice is between decontrol even without a tax and continued controls that will, with any further slight tightening of the supply, promptly bring back the gasoline lines. Decontrol is preferable.

People sometimes defend the controls by describing gasoline as a necessity of life. But the price of food is not controlled, or the price of clothing or medicine or, for that matter, heating oil -- all of which, on the list of necessities, rank a little higher for most people than gasoline. If Mr. Carter wants to see another significant drop in gasoline consumption, his best course is to use his present authority and the international moment and let the price go up now.