DO DREAM CARS REALLY COME TRUE? `Cars of the future' help automobile manufacturers test public opinion as well as new engineering concepts

YOU'VE seen them at auto shows and sighed over their 21st-century aura and design. Yet few people ever get the chance to sit behind the wheel, step on the gas pedal, and go. They're the ``idea,'' or concept, cars that allow the imaginations of the new-car designers to fly. The Pontiac Pursuit, for example, is an exciting four-place coupe, but it will never be caught in rush-hour traffic. It's the culmination of a bunch of far-out ideas in steel, plastics, ceramics. Its only purpose is to point the way in auto design, outlandish as it may look in 1987.

Terry Henline, chief designer in Pontiac's Studio One, describes the Pursuit as ``a little like holding up a mirror,'' where Pontiac designers are testing not only themselves, but also the reaction of the public to their efforts.

As you might suspect, building an idea car isn't a small-change pursuit. It can involve tens of thousands of man-hours and cost up to $2 million or more, says Mr. Henline. Yet, he adds, it saves money in terms of the design process itself.

All carmakers produce concept cars - well over a hundred in the last 40 years - although some are far more creative than others.

The 1967 Ford Seattle-ite XXI had six wheels - two in the back and four in the front. Instead of a steering wheel, the car had a finger-tip-controlled steering dial, which was mounted on a console between the driver and passenger. It even had a computer screen that gave the driver a whole lot of data, including the weather and estimated time of arrival.

The Chrysler Norseman, built in Italy in 1956, was aboard the Italian liner Andrea Doria when it sank off the coast of Massachusetts. The car, complete with (have you guessed?) tail fins, had a novel way of supporting the roof, and all major body panels were aluminum.

The '59 Cadillac Cyclone had radar in two large nose cones in the front fenders. Automotive engineers are still working on the idea.

The 1951 Buick Le Sabre had a convertible top that would automatically close, and the windows roll up, when rain hit a sensitized spot between the seats. There was even a proposed atomic-powered vehicle called the Nucleon, built in 1969.

But back to today and the onslaught of new show-car metal: Mitsubishi showcases its MP-90X with its black-glass canopy from front to back. France's Peugeot displays its Proxima, while Subaru points to its ``concept car of the near future,'' the ACX II, based on the Subaru XT.

Porsche talks about its P.E.P., or Porsche Experimental Prototype, now being run on the West German carmaker's test track. The modular-built test vehicle, the company explains, is aimed at exploring the dynamics of an array of basic vehicle layouts. Chevrolet puts forward its 150-m.p.h., low-drag Express as an option to short-hop airplane travel (but who will build the high-speed roads for it to ride on?).

Ford has learned a lot about aerodynamic design from its continual evolution of its Probe cars, now up to five and counting. ``As we learn something on these advanced models, if feasible, we apply it to our next-generation cars,'' says Donald Kopka, retired vice-president of design at Ford.

A Ford idea car of a few years ago had an electronic transmission that was controlled by ``piano keys'' on the steering wheel. Another system involved voice commands to open the hood or trunk, turn the lights on or off, lock or unlock the doors, and even start the engine from a remote location. Simply speak and the car obeys.

Who comes up with these designs? It's the futuristic design crews who yearn to be unique. Concept vehicles, in fact, are designed to spark the imaginations of producer and car buyer alike.

No one expects a mass-produced Pontiac Pursuit to make it to the real world, nor should it. Yet bits and pieces of it may well be channeled into cars of the mid-1990s and beyond, according to Pontiac engineers.

After a little time behind the wheel of the Pursuit, this writer predicts it will take a long time indeed for a motorist to really feel at home in such a car. The four-wheel electronic steering is computer controlled, so there is no mechanical link between the wheels and the steering wheel. The skirts that cover the steering wells move mechanically, however, as the wheels turn.

Admittedly, all these concept cars are not really ``cars of the future'' in themselves, yet they are directional markers for today's car designers as they peer down the road.

Looking ahead, the car creators see:

Wider use of four-wheel steering and full-time all-wheel drive.

Active suspensions that control the pitch and dive as well as the body roll of a car. Height sensors will adjust the ground clearance to the condition of the road.

Fender skirts that move as the wheels turn, thus further reducing the air drag on a vehicle and improving its performance.

Cathode-ray tubes to replace the conventional instrumentation.

A dashboard navigational system that will help the driver pick his way through a confusing maze of roadways in unfamiliar territory.

A heads-up display of instrumentation on the windshield, such as is now used in some aircraft.