For more than a dozen years now, the state of Virginia has quietly and conscientiously been searching out its most scenic roadways, awarding them the official designation of "Virginia By-Way" and highlighting them in forest green on the Official State Highway and Transportation Map.

To date, there are 16 such byways, mostly two-lane winding back roads away from heavy traffic. Like Rte. 39, which spills out of the Allegheny Mountains into Lexington as if it were a rushing stream, they are among the most inviting drives in this region.

Some routes are quite short -- no more than 10 miles -- but still well worth a detour. Others located in historically rich areas -- for example, Rte. 5, the James River route from Richmond to Williamsburg -- make agreeable destinations for travelers interested in a weekend getaway. Many are in the mountains where summer's lush green foliage will shortly take on the brilliant hues of fall.

West Virginia also has made a strong effort to spotlight particularly lovely drives -- the Highland Scenic Highway south of Elkins is magnificent -- but its roster of special byways (about a half dozen) isn't nearly as extensive as Virginia's. Only the Highland Scenic Highway is named on the official state highway map, but the official state guidebook and state tourism officials can direct you to the others. A scattering of red dots on Maryland's state highway map, particularly in the western panhandle, indicate scenic overlooks, and a short stretch of U.S. Rte. 40 in Allegany County is marked as "scenic."

As it happens, Virginia also is graced by three well-known federal scenic highways: Skyline Drive in Shenandoah National Park; southwest from Shenandoah, a lengthy stretch of the Blue Ridge Parkway; and the Colonial Parkway, linking the historic colonial communities of Yorktown, Williamsburg and Jamestown. Wonderfully scenic, the parkways nevertheless roam a landscape mostly empty of permanent inhabitants. The state byways, on the other hand, dip repeatedly into the everyday life along Virginia's back roads.

Virginia has been naming byways since 1974. The first was Rte. 193, the Old Georgetown Pike heading west for 12 miles through wooded hills from McLean to Great Falls in Fairfax County. Though hardly a back road even then, it has been followed by considerably more remote byways throughout the state.

Private citizens or local governing bodies can nominate favorite routes as official byways, and then the nominees must progress through a formal approval process that involves both the Commonwealth Transportation Board and the Department of Conservation and Historic Resources. Highway department officials inspect the routes to determine if they have "significant esthetic and cultural values" and if they lead to or lie "within an area of historical, natural or recreational significance."

The official designation of byway is awarded by the Commonwealth Transportation Board. Then Virginia By-Way road signs are erected, and the routes are marked in green in the next edition of the state highway map. If the roads eventually need rebuilding or improving, special care is taken to retain their appeal. But if they become congested or unsightly development intrudes, the byway classification can be revoked.

Other than the map -- available free at state tourist offices -- there is no guide to Virginia's byways. The next time you plan a trip in Virginia, pay heed to the map's green lines and consider routing your journey over one or more of them.

Among the possibilities:

Goshen Pass, Lexington: Perhaps the most delightful of the byways -- as much fun as it is scenic -- is the 56-mile drive west from the historic city of Lexington into the Allegheny Mountains. The road climbs alongside the Maury River, a rock-filled white-water thriller that -- in places -- calms down sufficiently to permit swimming and tubing. Many people sun themselves on the rocks, dangling their feet in the river.

The river route to Williamsburg: Once an Indian trail, Rte. 5 along the James River was later the main road between the state capital at Richmond and the colonial capital at Williamsburg. Long ago bypassed by U.S. Rte. 60 and then I-64, the 50-mile route passes through countryside that still offers glimpses of the 17th and 18th centuries. Perhaps the most historic of Virginia's byways, it winds through Civil War battlefields outside Richmond; approaches several James River plantations, including Berkeley; and ends at Williamsburg and Jamestown, which is the oldest permanent English settlement in America.

Crabtree Falls, Montebello: For a very nice 65-mile circle drive out of Waynesboro, first head south for about 30 miles on the Blue Ridge Parkway. The views from the ridge-line are grand, and there's an interesting self-guided tour of a reconstructed mountain farmstead at the Humpback Rocks Visitor Center. Near Montebello, turn east on Rte. 56, a splendid byway that dips and twists like a roller-coaster as it races from the mountain top to the valley. Along the way, plan to stop at Crabtree Falls in George Washington National Forest, the state's most eye-pleasing waterfall. A short trail takes you to its base, and a two-mile trail leads to the top. Return to Waynesboro via Rte. 151, another byway that winds through the Blue Ridge foothills, offering views up the mountainsides.

Burkes Garden, Tazewell: If you find yourself in the mountains of southwestern Virginia, let yourself be tempted into exploring the shortest of Virginia's byways, 10 miles of Rte. 623 running southeast from Tazewell. Phil Baker, a landscape specialist for the highway department who has driven all the byways, considers it one of the loveliest. There are excellent mountain views as the narrow road finds its way into the remote mountain-ringed valley of Burkes Garden.

Among West Virginia's roadways that have been recognized for their beauty are these three mountain routes:

Highland Scenic Highway: A gorgeous mountain drive, the 23-mile Highland Scenic Highway (Rte. 150) in eastern West Virginia meanders through some of the state's finest scenery. From the Cranberry Mountain Visitor Center, which provides information about hiking and camping in surrounding Monongahela National Forest, the two-lane highway climbs to 4,600 feet, a realm of windblown crags. Then it dips back down again, still offering fine mountain vistas, to the Williams River.

Highland Trace: Though its official status is in question, the Highland Trace is nonetheless a stunning drive. Meandering for about 165 miles through the mountainous Potomac Highland region of eastern West Virginia, it manages to pass near many of the state's natural treasures -- among them, the towering Seneca Rocks -- as well as Snowshoe and Silver Creek ski resorts. The trace follows Rte. 55 west from Wardensville on the Virginia border to Elkins, and then turns south toward the Cranberry Mountain Visitor Center. There it swings west again to its terminus at the tiny community of Muddlety.

Elk River Scenic Drive: In the mountains north of Charleston, Rte. 4 scrambles alongside the Elk River for 30 refreshing miles between the small towns of Clay Junction and Servia.

BOARDSAILING HOLIDAYS: At the Sailboard Center in Sebastian, Fla., Burr and Patty Hazen have put together a weekly package that includes lodging, all meals and six days of sailboard lessons. They have dubbed it "bed, board and board."

Limited to nine participants, the fall-through-spring learning weeks are open both to beginning and more-experienced sailboard enthusiasts. Classes begin Saturday at noon and end the following Friday morning.

It's a group experience devoted morning to night to sailboarding. Participants stay in a large restored roadhouse (rooms with shared bath) and take their meals together in the dining room. Lessons with certified instructors during the day are followed by video reruns in the evening. Attire throughout the week is T-shirt casual.

Sebastian is just north of Vero Beach on Florida's east coast. Lessons are held on the Indian River at the Wabasso Causeway, which the Hazens describe as "a large body of water a mile inland from the Atlantic Ocean." The average depth is about four feet, which, they say, makes it an ideal spot for beginners. However, first-timers start their lessons using an on-land sailboard simulator.

The price for the week is $550 per person, which also includes use of a sailboard. Single participants may be asked to share a room. The minimum age limit is 16.

For information: The Sailboard Center, 9125 U.S. Rte. 1, Sebastian, Fla. 32958, (305) 589-2671.

"2 FOR 1" TO TAHITI: United Airlines frequent fliers with 10,000 miles in their account are eligible for Air France's "2 for 1 Fall Sale" on round-trip flights from Los Angeles to Tahiti. Buy one ticket at any fare level -- first, business or economy -- and the second ticket for a companion is free.

The offer is good from Sept. 4 through Dec. 12. The economy fare for the eight-hour, nonstop flight from Los Angeles currently is listed at $849, based on a 14-day advance purchase. There is an additional fare of $320 each for both travelers for the connecting round-trip flight between Washington and Los Angeles. Air France departs Los Angeles twice weekly on Monday and Friday at 4:55 p.m. The return flights are Tuesday and Saturday morning.

AIR COURIERS: Travelers with flexibility can sometimes save up to 50 percent or even more on air fares -- domestic and international -- by taking on the limited duties of an air courier. One catch is that you have to make do with only carry-on luggage, since the courier company will be using your baggage allotment.

A seminar in how to sign on for courier service has been scheduled by First Class, an adult education organization featuring informal self-help classes. It will be led by Kenneth Clarke, who is described as a veteran air courier who has operated a courier service in New York for five years.

Entitled "Flying Cheap as an Air Courier," the seminar will be held Monday, Sept. 21, from 6:30 to 9:30 p.m. at the First Class office, 1522 Connecticut Ave. NW. The fee is $28 plus $2 for materials.

For information: 797-5102.

LUXURY FREIGHTER: In February, Ivaran Lines will introduce a 108-passenger cruise ship, the Americana, that will double as a working freighter. Bound for the South American trade, it will make 46- to 48-day round-trip voyages out of New York.

One aim in launching the ship, according to the freighter company, is to "put the romance back into cruising." Passengers will be treated to such comforts as a swimming pool, health club and lounge. But the Americana will not offer "the regimented schedule of daily activities and theme nights that make many cruise ships more like floating carnivals." There will be a single seating for meals.

The Americana is unusual in that it will be the only freighter sailing from the United States with more than 12 passengers, says Ivaran. Most freighters that carry passengers from U.S. ports take only 12, the maximum permitted without a doctor aboard. The Americana will have a doctor.

From New York, the Americana will call on Charleston; Savannah; Jacksonville; Miami; Rio de Janeiro; Buenos Aires; Montevideo; the Brazilian ports of Rio Grande, Santos, Bahia and Fortaleza; and Norfolk, Baltimore and Philadelphia.

The fare for the full seven-week cruise is $7,200 for an inside single cabin; $8,400 for an outside single cabin; $9,000 per person for a double outside cabin; $10,500 per person for deluxe double suites; and $16,800 per person (double) for the owner's suite.

For information: Passenger manager, Ivaran Agencies, 1 Exchange Plaza, New York, N.Y. 10006, (212) 809-1220.