The recent burst in the number and variety of category-bending vehicles struggling to find a sweet spot between minivans, truck-based SUVs and sedans will only intensify in the wake of shifting buyer tastes and surging fuel prices.

The cost of a fill-up may be on the rise, but that doesn't mean demand for functional people-carriers is shrinking. The trick, says Wes Brown of the market research firm Iceology, is that mainstream, middle-class "people don't want to drive minivans and luxury buyers are tiring of SUVs."

Or as one designer put it at a recent auto show: "We're desperately trying to reinvent the station wagon. It still has such a negative image connotation, and yet it's such a practical design."

Thus the explosive growth in sales of so-called "crossover SUVs" as varied as the Chrysler Pacifica, Honda Pilot and the coming 2006 Subaru B9 Tribeca. Last year, sales of car-based utilities outpaced the growth of SUVs based on truck underpinnings, and that trend is continuing in 2005.

Not surprisingly, the auto makers are rushing to meet the growing demand with new models that blur the boundary between traditional cars, SUVs and minivans.

At the luxury end, DaimlerChrysler's Mercedes-Benz brand will introduce its U.S.-assembled R-Class wagon this fall. The R-Class is as long as a large SUV, seats six in executive-class comfort, but rides low to the ground like a luxury sedan. A super-sized rear door makes for easy access, but it doesn't slide like a minivan's doors.

For the greater number of buyers on budgets too tight to accommodate a Mercedes R-Class, there is an obvious shift toward smaller SUV-like vehicles, such as theMercedes B-Class, expected to be priced in the $30,000 range when it arrives this fall. And, of course, showrooms already have the $20,000-something Kia Sportage and its kissing cousin, the Hyundai Tucson, which are good examples of the newest, affordable car-based utilities. More like them are coming, too.

General Motors' Chevrolet brand will begin selling later this year a new compact wagon called the Chevrolet HHR. GM officials say the HHR is modelled after a 1940s Chevrolet Suburban, but its fuel-efficient four-cylinder engine is not nearly as thirsty as anything that has powered a Suburban.

As for the minivan itself, Ford officials suggest it, too, may evolve into something very crossover-like. A good hint at Ford's thinking there can be found in a show vehicle called the Ford Fairlane -- a name taken from a Ford sedan of the past.

Ford design chief J Mays says his designers have concluded that a next-generation people mover "should not look like a minivan and it certainly should not be an SUV. Both of those vehicles have some negative baggage tied to them."