THE SUPREME COURT decision upholding Arlington County's ordinance against commuter parking is good news for rational urban planning. The way is now open for cities to deal intelligently with the role of the automobile - specifically the commuter automobile - in problems concerning air pollution, noise, congestion, safety and litter. If the Court had accepted the logic of the Virginia Supreme Court, which held the ordinance unconstitutional, the task of the cities would have been complicated enormously.

We never understood why the Virginia court look at this case the way it did. It decided, unanimously, that the 14th Amendment was somehow offended if a community discriminated among motorists through commuter-parking bans. The ease with which the Supreme Court disposed of the case - reversing without bothering to hear arguments or ask full legal briefs - suggests that the Justice didn't think much of that lower court ruling either. And the language of the Court's opinion indicates that it is prepared to get local governments draw many kinds of distinctions between what various groups of citizens can and cannot do so long as the distinctions are reasonably related to the creation of better environment.

Ordinances much like that in Arlington are already in effect in the District of Columbia and several other cities. Presumably, a similar ordinance on the books in Montgomery County will noe be brought into operations since the doubts about its validity have been resolved. All these are designed to keep commuters from parking all day on the streets of specified residential areas and to encourage residents as well as commuters to go to work by public transportation. Restrictions of this kind are a key part of the program recommended by the Environmental Protection Agency to clean up the air in urban areas by discouraging automobile commuting.

No doubt there will heavy pressure on many local governments to restrict parking and, for that matter, traffic in a great number of residential areas. And there will be a great deal of anguish among those who have been parking in those areas after driving to work or to reach a bus or subway stop. Part of the task will be to strike a workable balance. If a community wants to keep commuter autos offresidential streets, it will probably have to provide parking close to transit stops; otherwise, commuters who lived beyond walking distance of those stops are likely to end up driving all the way to work, instead of part of the way, and creating even more of pollution that ordinances of this kind are designed to curtail.