SOME OF those who are girding for Greater Washington's Grand Gridlocks of Tomorrow are noting that transportation issues do not stop at the borders of any one jurisdiction. If the various local governments are to deal effectively with questions about roads, rails and sky traffic in and around the metropolitan area, they should consolidate their policy-making. While some agencies have joined up to tackle certain issues, these regional efforts by and large have failed to keep pace with the changes taking place from center city to well beyond the Beltway.

Anybody who looks down the pike from, say, the outermost boundaries of Fairfax or Montgomery counties can practically see the waves of the future: waves of cars, trucks, rail cars and whatever else is built to move people and goods. This is what has prompted two regional proposals that deserve public understanding: one is from Greater Washington Board of Trade President Edmund B. Cronin Jr.; the other is from Fairfax County Board of Supervisors Chairman John F. Herrity.

In a speech last week to the Kiwanis Club of Washington, Mr. Cronin took stock of the number of agencies dealing with transportation in the region. "It's enough to make your head swim," he commented, calling for creation of a metropolitan area regional transportation authority with all the "necessary authority and accountability for coordinating and carrying out major transportation functions." He urged Maryland Gov. Schaefer, Virginia Gov. Baliles and D.C. Mayor Barry to begin the organizing, noting that enormous amounts of money are involved.

More immediate -- and as one preliminary to a region-wide authority -- is the proposal that Mr. Herrity first made more than two years ago and that won unanimous approval of the supervisors yesterday: the creation of a Northern Virginia Regional Transportation Authority that would extend beyond that of the current Northern Virginia Transit Commission. The idea is to team up with the outer counties to coordinate park-and-ride connections to mass transit, commuter rail service, the routing of motor vehicle traffic, road projects, bus service, HOV-lane extensions and plans for an outer beltway -- anything to do with transportation.

Officials from the various jurisdictions hope to produce the necessary legislative recommendations for approval at the 1988 session of the state legislature. At the rate Northern Virginia is growing -- and reaching outward for still more living space -- next year would be none too soon.