Your average truck driver just isn't built like Brooke Shields. And Calvins just look sooo tacky surrounded by an 18-wheeler.

So Jonbil Inc. of Chase City, Va., has just the thing: designer jeans for truckers, roomier in the thighs and seat with extra-large pockets, tough stitching, and built-in stretch for comfort on those long hauls.

In fact, that's the name on the label: Long Haul. And the jeans are racking up sales for Jonbil that would impress even Gloria Vanderbilt.

Don't go shopping for Long Hauls in your local boutique or Bloomingdales. They're only sold at--you guessed it--truck stops, at a suggested retail price of $19.99.

"The response we have gotten since they went on the market in the beginning of September is just phenomenal," says Marshall Bank, vice president of Jonbil, a small, privately held jeans manufacturer. The company is projecting first-year sales of the jeans of as much as $3 million--a good chunk of Jonbil's total revenues of about $25 million.

The success is perhaps as attributable to aggressive marketing as it is to a good idea. Jonbil has been advertising the jeans in truckdriver magazines like Overdrive in ads festooned with buxom women in tight T-shirts with the distinctive Long Haul stagecoach label. Bank describes the ads as the type that drivers "like to look at--which include one to three blondes.

"There's nothing banal about it," Banks adds. "They happen to be quite tasteful ads that have some beautiful girls in them." Actually, Bank seems a little bemused by the challenges of catering to the semitrailer trade rather than the carriage trade. "This is a totally strange market," he says.

The success of the jeans has led to a growing array of Long Haul merchandise--after all, what are designer labels for? The T-shirts worn by the models in the ads proved so popular that Jonbil began selling the shirts, and has now added denim caps. Coming soon are Western shirts, belt buckles and maybe even a vest, so the truckdriver can be dressed almost head to toe in Long Haul garb as he sits behind the wheel of his Peterbilt.

Or her Peterbilt. Jonbilt also markets the jeans in women's sizes, along with men's in waist sizes from 28 inches to 54 inches.

Jonbil, which mostly makes private-label jeans for department stores like Sears, J.C. Penney and Montgomery Ward, got the idea for truckdriver jeans in conversations with a buyer for one of its customers, Bank says. "We took the thinking a little forward and developed it into the concept of a specialized jean and apparel for the truck driver," he says. "This is the first time that somebody took a look at this market and made apparel for it."

The company talked with truck drivers and truckstop operators and found out the truckers felt kind of pinched in their Lees and Levis. "The truck driver himself is a larger guy, typically," Bank says. "So what we did was we increased the seat and thigh areas so they would fit the body. It was a utilitarian style with a touch of fashion."

But the secret of the jeans' comfort lies in their stretch, the result of a 31 percent dacron polyester mix in the denim. Stretch jeans have been around for years without ever really catching on, but Bank thinks Jonbil has hit on a marketing gimmick that will correct that.

Jonbil--which is mulling requests from big department stores to take the new jeans to the general public--is already looking for new markets for Long Haul-type jeans. On the drawing board are wide-cut stretch jeans for construction workers.

What designer label will those bear? What else: Hardhat.