Maryland transportation officials are studying whether to build a major highway several miles outside the Capital Beltway from Rte. I-270 at Rockville to the Baltimore-Washington Parkway in Prince George's County.

The 32-mile highway would cost an estimated $262 million if it included a southern spur that would extend for about five miles along Montrose Road at the southern edge of Rockville.

The highway and the spur are needed, said Michael W. Waldron, a planner at the Maryland-National Capital Park and Planning Commission, because, "you can't improve the Capital Beltway any more. We've gone as far as we can go on Randolph Road (a cross-country artery). There are bottlenecks that can't be improved."

While the Maryland Department of Transportation has not taken position on the highway-that will come after the study-the project has the strong backing of Montgomery County planners, including Waldron, on the park and planning commission.

The highway proposed for the Maryland suburbs and the proposed Springfield bypass that would arc about 30 miles from Rte. 7 south and east to Rte. 1 in Fairfax County both would be major cross-county routes, recalling the once planned outer beltway.

The outer beltway, which would have circled the metropolitan area beyond the present Capital Beltway, was seemingly scrapped in the early 1970s as unnecessary and too expensive.

If the Maryland highway and the Springfield bypass were both built, a major portion-although considerably less than half-of what would have been the outer beltway would be created.

There would still be no links between the Baltimore-Washington Parkway across the Potomac River south of Washington to Rte. 1 and from Rte. I-270 across the Potomac northwest of Washington to Rte. 7.

The latter of those missing links-from I-270 to Rte. 7-is exhibiting at least faint signs of life. It is still on Montgomery County's master plan for the Potomac-Travilah area and, according to Waldron, has the strong support of Montgomery planners.

According to Loudoun County planner Milton Herd, Montgomery planners recently lobbied Loudoun officials to throw their support to the extension. In the past, Loudoun opposed the outer beltway, and Herd said the issue hasn't been reexamined recently.

The project under study by the Maryland transportation agency does not include a link to I-270, and according to Waldron, land reservations in the area have lapsed since they were obtained by the county years ago when the outer beltway seemed a likelier possibility.

James Helms, assistant project manager for the Maryland study, said that if analysis favors the highway, possible alignments could be presented to the public in the fall. He said extensive rights of way-obtained when the outer beltway was first envisioned-are still intact.

Even if both the Montgomery-Prince George's road and the Springfield bypass win approval, their financing is less than certain. Both projects would count heavily on federal funds, but since neither would be an interstate road, U.S. money would be limited. One Federal Highway Administration official estimated that if Virginia and Fairfax were counting on federal funds for the bypass, the proect could take 20 to 25 years.

That would lea ve most financing up to each state and the affected localities. However, neither Maryland nor Virginia has budgeted all or even most of the funds that would be required, and each locality says it is already stretched to the limit to finance present projects. CAPTION: Map, Dotted line indicates connector highway and spur being studied by state. The Washington Post