Trevor Thomas recalls, with only a little bit of pain, his run-in with a small sports car.

Rollerblading at breakneck speed down Newbury Street, Thomas as brought to a painfully abrupt halt when the door of a parked automobile swung suddenly open, placing a steel wall directly in his path. The 19-year old managed to escape massive injury by dragging one skate sideways behind him to slow down and breaking the inevitable crash with thrust-forward arms.

"That was pretty heinous," Thomas muses.

Thomas took three days off from skating to let his smashed wrists recover. Now he's back on his Rollerblades, dazzling the spectators that line Memorial Drive along the Charles River on sunny Sunday afternoons.

A 200-yard section of the street is given over every Sunday to a complicated obstacle course of traffic cones. At one end of this maze lies the showpiece, a three foot high wooden ramp. Trevor occasionally soars off this slanted plane, putting up to seven feet of air between himself and the ramp.

Zigzagging through all of this are dozens of skaters, some novices out for a Sunday challenge , others, like Thomas, sporting a bright yellow "Team Wiley" T-shirt. "Don't try this at home," the shirts' logos appropriately warn.

Team Wiley is the creation of Sharon B. Weil. Weil worked for Rollerblade until six months ago, when she quit and decided to start a team to give exhibitions and compete with other squads. She started scouting at Boston's Esplanade for talented skaters, and later held auditions to find the skaters with the most flair and skill.

Surprisingly, many of the best skaters were newcomers. Thomas bought his first pair of blades eight months ago when he totaled his motorcycle ("I had no other way to get around," he explains), and 15-year-old Chuck J. Mello, the team's youngest member, learned to skate just five months ago.

In this short time, these skaters have developed an improvisational, fresh style.

"We do freestyle, street-style, crazy, stupid, stuff," Weil says. "It's a ball."

The skaters dart backwards and forwards along the river, effortlessly combining powerful speed and delicate, intricate footwork. Members of the team lock arms and glide through the cones in a line, periodically unlatching and reassembling. The swaying motion is almost hypnotic.

People are more than willing to pay for this entertainment, and the team has been booked for Boston's Fourth of July Celebration, where Weil says more than half a million people are expected. For the highlight of that show, Thomas will jump off the ramp and sail over a Honda Civic.

It's not all glitzy moves, though. Rollerblading has its less pleasant side, as most of the Sunday skaters can attest. Thomas' type of accident is a common occurrence for almost any frequent skater.

Weil "took a major dive" last summer and bruised her spine. Mello wears a jagged scar on his neck obtained recently when he skated through a clothes line in a nearby alley. Victor Luke, 28, sports, wounds on both elbows and knees in various stages of healing.

And Nancy McGinty, a recreational skater who sometimes watches the riverside displays, badly bruised her knee when she fell on her icy driveway, and was sore for four months. Now she wears knee pads. Watching the skaters' hot-shot antics, she shakes her head in amazement.

"Kids have no fear," she says.

That overconfidence sometimes worries Weil. Although she's convinced her team to wear knee and elbow pads when they practice, helmets are still unpopular.

"They should wear helmets. They don't she says simply.

Luke, who likes to skate in traffic ("It's the adrenaline"), says "I definitely think you should wear [a helmet]. I don't wear it myself, for aesthetic reasons."

Another source of problems have been with bike riders. Nearly every rollerblader has some story to tell about antagonistic bicyclists. Many skaters say that the cyclists resent them for increasing their numbers so greatly and so quickly.

"We get a lot of friction," Weil says. "I've seen bikers intentionally knock skaters down ... and curse them out. I've had people elbow me."

"They go really fast, then they hit you and it's your fault," Thomas adds.

But Luke says tension is wearing off as bikers become resigned to the presence of the rollerbladers. "They've learned to accept it. There's more of us," he says. "People are ignorant of [the sport] until there's too many skaters to handle."

Rollerblade is actually a brand name that has, Kleenex-style, become synonymous with the type of product itself. Those in the know call the contraptions "in-line skates" to distinguish them from their passe cousins, roller skates.

In-lines were originally conceived of by two hockey-playing brothers from Minneapolis who wanted a way to keep in shape during the off-season. Scott and Brennan Olson built the first pair of in-lines in their garage in 1980.

The device enjoyed a limited popularity among hockey players until roughly four years ago, when sales abruptly and somewhat inexplicably skyrocketed. Mike J. Benshoff, Boston area representative for Rollerblade, attributes this lag time to cosmetics. In late 1988, Rollerblade developed a new skate with a flashy neon design, and sales started climbing. "When those went on the wall, things took off," Benshoff says.

Since then, Harvard and other Boston-area students have been among the most consistent consumers of Rollerblades. Benshoff reports that City Sports in Boston has sold over 3000 pairs of blades this year. And the company is still expecting three more years of growth.

Jim Brine, who owns Brine's Sporting Goods in Harvard Square, confirms the popularity of these toys. "There was a dramatic sales increase in 1991," Brine says. "And 1992 was much more dramatic than 1991." Brine says a number of factors help make the skates appealing to so many different types of consumers.

"Some of the people are joggers whose knees can't take jogging anymore," he says. "A lot of young people are playing hockey on them, not rellay for conditioning, just for fun." And in Harvard Square, students are buying them simply to get from one class to another. "You can cover a lot of ground." Brine says.

The demand has been almost too much for Rollerblade to keep up with, Brine says. Competitors like Ultrawheels, Bauer, and Roces are making quick inroads, and, in some cases, turning out a more durable product.

"On the low end, under $150, most of the Rollerblade boots are superior, but on the high end [it's] pretty close," Brine says, citing Roces' and Ultrawhells' use of a more durable wheel.

There is even a new skate on the market called Metroblade which includes detachable wheels a la Inspector Gadget. "You can go to work in them, take off the wheels and walk around," Brine says. But Brine is skeptical about the new product, which he labels as gimmicky.

"I don't know how much you'd want to do that. They look more like a roller blading boot than anything else, certainly no a stylish shoe."

But traditional blades will be in vogue or some time, Brine thinks. "It's here for a while," he says

The terminology of this relatively new sport is still in a protean stage. Fans describe the slippery move of the skaters in expressive, everyday language.

This lack of a firmly established insider's jargon makes the sport surprisingly accessible to newcomers. There is no esoteric nomenclature to be committed to memory before truly understanding rollerblading. Anyone can talk about it.

"May favorite thing Trevor does is when he starts skating pretty slow and then smashes into the curb and uses the momentum from the crash to do a front flip and lands back where he was," says a wide-eyed Aurora Lucia, 11, who often sees the team practicing where she skates.

"I like it the way Victor spreads his knees apart and then goes up on his front wheels only and goes backward through the cones zigzagging really fast. That's rad," says a friend nearby.

The skaters themselves are sometimes at a loss to describe in words what comes so naturally to them on wheels.

"I do this trick in the show ... sort of a sideways criss-cross thing ..," Victor trails off. Frustrated, he gets up and demonstrates what he means: starting with his feet in first position, he weaves them back and forth and somehow propels himself sideways through a series of traffic cones. The bright orange beacons flash in and out of view rapidly as his legs work through them, churning like an egg inch as he threads down the line. The move speaks for itself.