The U.S. TRAVEL industry approached Independence Day 1979 with a sense of dependence, frustration and concern. For an industry that depends upon mobility for its economic survival, the question recently has been not "Where are we headed?" but rather "How far are we going?" - and sometimes even "Are we going anywhere?"

The gas crunch is the major deterrent, but inflation and a sagging economy are growing factors. Yet the travel business up to now has been generally in good helath and some sectors, like cruising, have been booming.

Travel is one of the top three industries in almost all of the 50 states. Industry figures indicate its supports about 5 million jobs. Billions of dollars are involved.

While airlines, cruise ships, buses and railroads are still transporting tourists, many hotels, motels, restaurants, amusement parks and other attractions remain heavily dependent upon the automobile to transport a large percentage of their paying guests. Hotel chains and state tourist agencies are trying to calm visitors' fears. (See Elizabeth Mooney's Weekend column for the effect of the gas shortage on one small nearby town, and her story on Page F6 about steps being taken to provide up-to-date reports to drivers. Also, the story on Page F3 by Melissa Davis about how rental car companies are faring.)

Harried travel agents, still wrestling with the formidable job of accommodating confused airline passengers in the wake of the DC10 grounding ("it's across-the-board rerouting," according to Washington agent Andy Spielman), are now faced with clients' worries about finding gas for ground transportation both here and abroad.

Because of the time delay caused by Sunday production requirements, stories in the Travel section about the gasoline shortage cannot fully reflect the fluctuating energy situation, though they do provide useful comparisons and tips.

Therefore, in planning vacation travel by car this summer of our discontent, motorists should consult the daily paper, auto clubs, and state tourism officials for current information on the supply of fuel. For example, since reporter Markowitz returned from his cross-country motor trip, gas lines have shortened in some areas as a result of odd-even and other regulations, but energy problems have now spread from both coasts to other sections of the United States.

And though the National Park Service declined to give any predictions about the availability of gas to motorists visiting the park system this season, a spokesman here said that recent attendance figures for Grand Teton National Park show travel there "is about normal for this time of year," and the park reports a "higher percentage of advance reservations" than last year. "The number of cars in the parking lots is about the same" and the campgrounds are busy but not filled."There's plenty of gas and no lines at Grand Teton," the spokesman said, adding that concessionaires who pump gas inside the park "got 95 percent of last year's allotment." He noted that "of the 15 to 20 gas stations in nearby Jackson, Wyo., only one ran out of his June allotment." The main months for the park are July and August.

For those determined travelers who plan to visit one or more of our national parks, regardless of the price of gas or form of locomotion, the July issue of the National Geographic Magazine should be of special interest. The entire colorful issue is devoted to the parks, their past, present and future.