Driving, especially the kind we traditionally have done a lot of in the summer, isn't what it used to be.

Historians will likely mark the '50s,'60s and '70s as the Great Era of Free and Easy Motoring in the United States of America. Those were the days when gasoline was a bargain, station attendants were glad to see you, and the automotive industry constantly invited you out for a carefree highway trip -- practically an exercise of your constitutional rights.

Now, according to the American Automobile Association, automobile travel is dropping; it was down about 13percent in 1979. Americans who indulged themselves in the world's cheapest gasoline in that Great Era have sobered up on today's high and climbing prices.

Nor is driving all that much pleasureany more. The automobile remains No. 1 form of mass transportation in the United States, and most of us use a car instead of public transit to get to work. Egads, there are 144 million cars, buses and trucks in our republic! But weekend driving and those long hauls across the country have changed.

Cross-country motorists are never certain there is going to be a gasoline station open in a small town, especiallyat night. Sure, on the great interstate highways ther are oases of service. But nowadays travelers must make inquiries when dusk approaches, like wagon train leaders asking about the landscape ahead.

Gasoline stocks last month reached record-high levels, according to the American Petroleum Institute. Still, I see gas lines in the Washington area, and, when I am on the road, I even see them in small towns. The API explains that the lines are caused primarily by the government's price-control and allocation system, andthough we are currently glutted with gasoline, spot shortages and lines can result.

And so I see older people, their worn hands gripping the nozzle, filling up at self-serve, seemingly too timid toask the attendent to clean the winshield. Who would dare to ask for the tires to be checked and inflated properly, as all those conservation-slanted messages instruct us? Many stations don't even have air hoses anymore. Perhaps they are stored in the locked-up restrooms.

One of the great frauds of our time is that TV ad with that smiling gasoline station attendant, dressed as though he was ready to enter the operating room of a hospital, only he's really just brimming over with good feeling for you, the customer. The reality is that many of those fellows are either ornery or bored with customers, just taking their money or credit cards and waving them on.

Recently, I filled up at a self-service pump, and noticed that the prices were identical to those for full-service. The attendant just grinned and explained, "Some people like to fill their own tanks, so we let them, at the same price: Ha-ha."

Those pices have tripled since 1970. Every year up until 1979, a person had to work fewer minutes to earn the equivalent of a gallon of gasoline than he did the previous year, according to the U.S. Bureau of Labor Statistics. But the price now is running away.

For years we blamed OPEC, but actually OPEC's increases only matched the inflation of the Western nations and Japan. If you bought a gallon of regular in 1969, you probably paid about38 cents. Ten years later you paid about 80 cents -- double the amount -- but by then the dollar was worth only half as much as in 1969, so you were actually paying no more for gasoline in 1979. Now, in 1980, you are paying inflation-plus. But you're not paying $3 a gallon as the Japanese do, or eventhe $2.50 most Europeans do.

At least not yet. You really don't want to know it, but you still anticipate that gasoline will cost around $1.50 a gallon this summer, and perhaps $1.75 to $2 by the end of the year.

There is consolation in the fact thatthe new breed of cars will give you double or more the gas mileage of the cars of the '60s and '70s. So if you were paying 50 cents a gallon to operatea 15-mpg car in 1974, you were paying $3.30 for the gasoline to drive 100 miles. If you drive a new lightweight 30-mpg 1980 car, you will pay about $4.12 to drive the same 100 miles. Subtract the inflation factor, and you are probably ahead.

All this to be contemplated, calculated and hashed over before the family plans the big cross-country trip in the summer of 1980 -- the New Era of Practical Motoring.