It wasn't long ago that a single pair of sneakers was all that you needed to run, walk or jog. Today shoemakers have footgear for every imaginable activity and have most of us convinced that three pair are better than one.

Automakers may never be able to aspire to such a vision with vehicles, but the new wave of sport/utility vehicles (SUVs) now coming to market point out that the segment, like footwear, is becoming ever more narrowly defined.

"Consumers are continuing to define what it is that they want in an SUV," says George Murphy, Ford Div. general marketing manager.

Indeed. While SUVs offer some utility, buyers with a variety of needs have been forced to make a choice - particularly with Grand Cherokee- Blazer- and Explorer-sized vehicles - between passengers or cargo capability.

Ten years after Ford rolled out the Explorer, automakers finally appear to be catching on. Witness the Explorer Sport Trac, Nissan CrewCab, F-150 SuperCrew and Dodge Dakota QuadCab, plus the Chevy Avalanche concept.

"Everyone is looking for more versatility and more spontaneous usability," says Richard Parry-Jones, Ford's product development chief. "What people are looking for is the ability to mix and match load-carrying capability with passenger carrying capability. Actually, I am surprised in a way that we didn't think of this before."

Part pickup and part SUV, vehicles such as the SuperCrew and Avalanche are among a host of new "crossover" vehicles that combine the interior roominess of a full-size 4-door SUV with the convenience of a small pickup bed. While not for everyone, these new crossovers are expected to further boost SUV demand. Last year, they nearly doubled their share of light vehicle sales, finishing at 19.1%, from 10.3% in 1994.

"I don't think the SUV run will end as long as you give consumers what they want and need," Mr. Murphy says.

And right now consumers want car-like comforts with gobs of flexible utility. Spacious, reliable and functional are major characteristics sought by SUV buyers, based on a recent survey by The Polk Co. In households with children under age 18, functionality was rated as the most sought after characteristic in an SUV, even ahead of reliability; the same is true with other SUV buyers, too.

"These new SUVs are going to be especially attractive to families," says Karen Piurkowski, Polk's director of loyalty. "People are busy hauling kids on one day and then getting a load of lumber the next. We are moving in the right direction, but there still is a ways to go."

SUV buyers also are more likely to buy a second SUV, Polk says. Of those who purchased an SUV previously and then bought a new vehicle, 47% went home with another SUV. Pickup truck owners were second, with 15.8% likely to make a pickup their next new vehicle purchase.

"A key reason for the continued popularity of the SUV in America has to do with the active lifestyle many families enjoy," says Kim Pike, a Polk auto analyst. "For many, the SUV is the best product in the market due to its versatility."

While no one would ever describe the ride of Ford's Sport Trac as anything but truck-like, engineers made huge inroads toward giving the SUV/pickup not just versatility, but more car-like characteristics, especially in noise, vibration and harshness. This is important because Ford expects that many of these SUV crossover buyers will be coming from the car side.

This is a fact that hasn't been lost on automakers. Chevrolet's SSR (Super Sport Roadster) concept unveiled at the Detroit auto show last month began life as a car and then had some pickup characteristics added (namely a box), while the Dodge MAXXCab concept has some familiar minivan design cues with a small pickup bed that starts where a third row of seats typically would rest. It's a slightly different approach to what Chevy and Ford are offering, but the overall outcome is similar.

Same goes for Volkswagen's Advanced Activity Concept (AAC), a car-like vehicle with a small pickup box. The AAC focuses more on carrying passengers than it does cargo, but it's basically the same type of SUV/truck hybrid other automakers are racing to bring to market. VW isn't saying whether it will build the vehicle. But it does say some design features from the AAC could appear on the upcoming SUV being developed jointly with Porsche.

These new SUV crossovers may seem similar in appearance, but automakers are doing everything they can to tout any and all differentiating features. And with good reason. The SUV segment is expected to grow by some 26 new models over the next four years, swelling to no less than 70 offerings by 2005. This has automakers rushing to stake out an area along the SUV, pickup and minivan product territory lines that customers occupy today, rather than churning out a host of "me-too" vehicles.

For instance, Ford is bragging that its Sport Trac has a lockable three-piece hard plastic cargo cover that essentially turns the composite pickup bed into a large trunk. For those days when more hauling space is needed, Ford offers a stainless steel cargo cage (similar to the one used on Nissan's Frontier Crew Cab) that extends the box when the tailgate is down.

"Our extended load box was kind of the breakthrough thing for us," says Mr. Parry-Jones. "We can actually give customers both a reasonable load box, spontaneously reconfigureable, when they really need the extra length without the penalty of a longer vehicle that is less easy to garage (the Sport Trac is 1.3 ins. longer than Expedition). I think this type of vehicle is almost a natural outgrowth of the popularity of SUVs and the increasing use of pickups for people transportation."

Chevy took a different road with its Avalanche concept, based on the proven Suburban platform. While a hard tonneau cover is available, Chevy engineers designed a pass-through from the pickup box to the cab. The feature allows people searching for more cargo space to fold a panel in the back of the cab into the interior to create a cargo area that measures 8-ft. (2.4-m) long.

All of these new vehicles and concepts certainly fill a market need, but they only are made possible because automakers have cut new product development time and have factories that are more flexible. Building several types of vehicles on the same assembly line, which trims costs and makes a better business case for potentially smaller-volume vehicles, is helping drive development of these new SUVs.

That's one reason Ford's Kansas City Assembly plant in Claycomo, MO, will be able to build the new '01 Lincoln Blackwood in the fourth quarter.

Certainly, higher fuel prices and a softening light vehicle market could slow SUV growth, but many in the auto industry believe that isn't likely to happen, at least not any time soon.

W. Van Bussmann, DaimlerChrysler Corp.'s top economist, says SUV sales will continue to grow through 2005, but at a slightly slower rate than the segment currently enjoys. He says sales of larger SUVs are beginning to show signs of softening. "The bloom is coming off the (large utility) rose," he says.

As for price increases at the gas pump, Mr. Bussmann says that while the rise in gas prices may have had some effect on large SUV sales, a person who spends $30,000 on an SUV isn't going to worry about a few hundred dollars a year in added gas costs. "(Gas prices) are not a big part of the equation."