PRESIDENT CARTER'S DECISION to make federal workers pay market rates for parking is as good a sign as any that the administration thinks the energy squeeze is real. Thousands of federal employees have enjoyed free or low-cost parking so long that phasing out the privilege is bound to cause not just temporary grumbling in the ranks but to be received as a genuine deprivation. Yet like those famous symbolic limousines (which the Carter revolution summarily eliminated on taking office), the parking perquisites have become a kind of discordant note and signal in federal energy and transportation policy. As long as officials paid little or nothing for parking themselves, their appeals to the public to save fuel and use mass transit were less credible. Now Mr. Carter is saying: This time we really mean it-and we mean if for everyone.

The new policy could have real benefits. By one count, the executive branch controls parking for about 27,000 of the roughly 150,000 cars that stream into central Washington and Arlington each day. As the rent for those spaces goes up-to half the market rate Oct. 1, and to full commercial rates by 1981-more drivers should feel moved to form car pools or switch to mass transit. Besides saving gasoline, that will ease the strains on the region's highways and air. It will also bring the area's largest employer into line, at last, with the transportation and pollution-control policies that the Council of Governments has been struggling to advance.

Mr. Carter's order should be useful, too, in goading other employers around town to re-examine their own parking policies. Many private employers-including this company-provide subsidies of one sort or another that shield some of their employees from the full force of commercial car-housing rates. The most blatant freebies, of course, are on Capitol Hill, where Congree-despite excellent mass-transit service-has staked out nearly 9,000 free parking places and is constantly grabbing for more. Perhaps the law-makers will finally be embarrassed enough to start paying something for their parking privileges, although they enjoy on such matters what is perhaps the highest embarrassment threshold in the world. Finally, no list of laggards would be complete without the District City Council, which has arrogantly insisted on free parking for itself-even while demanding that federal officials pay.

The point is to make all commuters face the real costs and choices more squarely. That assumes, of course, that the choices as well as the costs are real. For thousands of commuters, one old argument for driving-that mass transit is inadequate-is much less plausible now that Metrol has reached the suburbs. But it is true that some people have few alternatives because bus and rail services is still poor in their areas or at their commuting hours. The government and other employers should give these workers some sympathy and some help. Federal officials keep talking about useful programs elsewhere-shuttle-buses, van-pooling and the like. They should get off the stick and try them here.