What is the hottest selling vehicle in the United States? Pinto, Chevette, Impala, Omni or Granada?

Wrong - it's the Ford pickup truck.

Ford sold about 819,000 pickup trucks last year, nearly half of the industry total of 1,857,000. Chevrolet was second with 746,000 and Dodge third with about 213,000.

Trucks sales rebounded from a sharp dip in the early '70's and have been registering strong and steady increases from just over a million in 1975 to an estimated 2 million for 1978.

The reasons for the truck boom include a marked increase in the number of women and young people who are buying them, according to industry sales executives, as a new sign of individuality and prestige.

While only 39 percent of all pickup truck sales in 1970 were for personal use, not commercial use, that figure has since swelled to 60 percent, according to Ford Motor Co. studies.

The growing interest of women buyers also has been recognized by Ford, which just issued a new truck manual "with primary emphasis for the woman reader," according to Ford's Marketing Plans Manager Michael Wood.

In many ways the truck has come of age. Almost every feature available power windows, power steering, electronic door locks, air conditioning, AM-FM stereo radios, bucket seats, and on and on.

And there are many features available to truck buyers that aren't available on most cars, like four-wheel drive and diesel engines. Plus, trucks boast a generally longer lifespan. Chevrolet advertises than 95.7 percent of all Chevy trucks sold since 1967 were still in use a year ago.

"What's we're seeing is the socialization of the truck," said Ford's Wood. "Product changes have brought the truck from behind the times. Why, until recently there wasn't even a space on a truck dashboard for a radio - now you can get every creature comfort you want."

Wood said that while the pickup is still a predominantly male purchaser other Ford light trucks are being sold to women in record numbers. An more and more women are becoming interested in the pickup, he added.

Ford's research figures show a dramatic increase in the number of young people buying trucks. Wood said, "Sixty-six percent of all four-wheel drive trucks now are bought by people under 35; 57 percent of all vans are bought by under-35s; and 10 percent of all pickups are bought by under 35s."

While the sale of Ford trucks has grown at a compound rate of 9 percent every year since 1967, car sales growth during the same period has been just 2 to 3 percent, Wood said.

Half of the pickups are still sold in rural areas, but metropolitan area sales are on the increase.

Said Wood, 35, who owns a Ford Bronco, "It's now nearly as quiet as a car, and in the end a heck of a lot more practical. It made me proud to help out during the blizzard, when truck drivers were running emergency medical supplies and handling problems that came over the CB."

Al Imber, Jr., is the Truck Sales Manager for Chrysler Corp., which makes Dodge Trucks. Although Dodge pickup sales lag way behind the Big Two, Dodge makes the top-selling vans on the market. Dodge truck sales in general are growing at a much faster clip than Ford or Chevy.

"You used to hear cracks like, "it drives like a truck,'" Imber said, "but all that has changed. Now trucks have become a symbol of esteem and prestige."

"The truck fills a social need," said Imber, "that used to be filled by hot rods for kids, and cars for their parents. With insurance rates going vans on the market. Dodge truck can be distinctive, and can be customized, and they cost less and are more practical."

"And now it is socially acceptable for a woman to drive a truck," Imber added. "Years ago a woman wouldn't let her husband park a pickup in the driveway because of what the neighbors would think. Now, not only do they put it in the driveway, but they take it to church."

Dodge studies show that the first-time truck buyer is about 30 years old, with a medium income of $15,000 a year. More than a third, according to Imber, are white-collar workers.

Still, Dodge promotion campaigns are aimed at the prestige sale. Calling certain models "adult toys," or "Macho," or "Warlock," Dodge specializes in the distinctive custom market, and will make more changes at the factory level than either Ford or Chevy to suit the needs of the individual buyer.

Chevrolet Motor Division National Merchandise Manager for Trucks is Richard L. Higginbotham, who has a two-color map of the United States behind his desk. The map is divided up into Chevy's sales regions, and says "Go Green," on it.

The 24 regions in which Chevy is ahead of Ford are colored green on the map, while the other 20 are red. But what is more important, the map supports what Higginbotham says: "Trucks are the hottest area of competition between Ford and GM."

Last year, GM's total truck sales, heavy and light trucks included, were 1,205,882 - which was about 8,000 short of Ford's total sales. And in three areas - Portland, Ore.; Fargo; N.D., and Salt Lake City - Chevy sold more trucks than cars.

The bulk of sales, about 90 percent, mini-pickups, campers, utility.The rest were heavy trucks, from "semi's" on down.

And light truck sales are becoming an even larger chunk of overall truck sales. One of the fastest growing segments of the truck market are 4-plus-4's, or four-wheel drive vehicles.

Both Chevy and Ford have entries in the compact, or mini-pickup, field. Both are made in Japan. Dodge, according to sources, is not far behond with its own entry. Dodge is expected - soon - to be the first auto maker to offer the mini-pickup with four-wheel drive.

Prices for trucks, like those of cars, vary greatly. A basic half-ton pickup starts around $4,500 list, reaches about $6,300 with a diesel engine. Four-wheel drive adds another $1,500 to the cost.

As the truck gets bigger (three-fourths ton or one ton), the price rises about $400 each step. Mini-pickups, which have extremely high mileage ratings (31 miles per gallon on the highway) run around $5,000 with few extras.

Prices on the various models of vans and trucks range from $3,500 to more than $10,000, depending on what extras are ordered.

The major problem facing the truck industry is growing pressure from the National Highway Traffic Safety Administration to improve fuel economy.

The NHTSA has ordered auto workers to produce trucks with a minimum 19.2 miles-per-gallon rating by 1980 - only three-tenths of a gallon less than the passenger car standard for the same year.

"It is completely unrealistic to require light-duty trucks which serve a variety of commercial and industrial purposes to achieve the same fuel economy as the family car," said Chrylser Vice President S. L. Terry at NHTSA hearings in Washington last month.

Terry and other industry spokesmen say that since the truck frequently has to perform work-oriented functions and is not just a pleasure vehicle, it is unreasonable to expect truck customers to forfeit power needed for jobs for better mileage.

In his comments, Terry told the NHTSA that the federal agency has "wrongly assumed technical improvements" in cars are readily applicable to trucks. "That is not the case," he said, "because trucks and cars are different."