Seated astride a sleek Honda 250 Rebel, a 21-year-old restaurant worker was participating in a class on motorcycle riding. Since he lived in the District and worked in Virginia, he hoped a motorcycle would provide inexpensive, convenient transportation.

One early exercise was deceptively simple. Shift to first gear. S-l-o-w-l-y ease out the clutch and give the engine some gas. Proceed at about 5 mph in a straight line. Head up and eyes ahead. Knees tightly hugging the tank. Right hand in a wrist-down position. Four fingers of the left hand covering the clutch.

"Engage the friction zone," shouted instructor Rick Nyman, who had previously told the class how a controlled release of the clutch averts stalling and adjusts speed.

But as the student started to put the machine in motion, he lost his balance. His instinct to pull back with his right hand caused the motorcycle to surge forward. Losing control of the bike, he scaled a 22-foot enbankment before falling off. Fortunately, no one was hurt.

"He forgot to cover the clutch," said William Morris, chief instructor for the California-based Motorcycle Safety Foundation, a dealer-sponsored group. Morris teaches classes at the Alexandria campus of Northern Virginia Community College. "If he was holding the clutch in as he engaged the throttle, he wouldn't have gone anywhere. He would have just made a lot of noise."

Coordination, dexterity, flexibility, balance. Attention. The ability to use four different limbs to perform four simultaneous activities. Practice.

Motorcycle riding can be challenging, fun and exciting. But it can be deadly for those who treat it like a toy.

In a study of 900 motorcycle accidents, more than 90 percent of the motorcycle riders involved taught themselves or learned to ride from family or friends, concluded a 1981 report by the University of Southern California Traffic Safety Center. The study called lack of training a significant factor in motorcycle accidents and said riders could benefit from specialized instruction.

"The leading cause of motorcycle accidents is alcohol and drugs," said Joann Bonkoski, manager of the emergency room at Prince George's General Hospital. "The prototype is a young male, in his early twenties, not wearing a helmet, doing 60 to 100 mph, drinking, taking PCP and striking either a bridge abutment or a telephone pole."

Of the 91 trauma cases reported in their emergency room last month, 15 involved motorcycle accidents, Bonkoski said.

Studies show that 40 to 45 percent of all motorcycle accidents that result in death involve alcohol. And there are about 50,000 alcohol-related motorcycle injuries each year, said Motorcycle Safety Foundation instructor Dominick Wasielewski.

Not all motorcycle riders, however, are young daredevils who drink and drive.

"I don't think the public has an accurate perception of cyclists," said instructor Morris, who is also a computer systems analyst for the federal Office of Family Assistance. "They think they are somehow on the low end of the social scale, reckless and a little loose upstairs."

The image of riders is changing. Suit-and-tie executives riding motorcycles to work are no longer an unusual sight. "Top-of-the-line Hondas and Harleys are between $8,000 and $10,000," Morris said.

Motorcycles are cheap to operate and easy to park in the city. They appeal to people with independent personalities who enjoy challenges. But there is a serious need for safer riding skills, Morris said.

Or as three-time world champion Road Racer Kenny Roberts is credited with saying: "Riding a motorcycle is 80 percent between your ears and 20 percent between your legs."

At the Northern Virginia Community College class -- one of a handful of area courses designed to promote motorcycle safety -- beginners learn that a motorcycle is much harder to drive than a car.

"In a car, you might be able to get away with taking your eyes off the road for a second," Morris said. "That is just not the case for motorcycles."

Students also learn that riders are less visible to car drivers and more vulnerable to injury.

"You don't have to be going very fast," said Dr. George Hajjar, director of the Emergency Service at Prince George's General Hospital. "If you are traveling at 20 mph and you hit something, the human body is not constructed to take that kind of damage."

One way to reduce the risk of injury is to wear protective clothing, said instructors Nyman and Wasielewski. Such clothing includes a helmet, sturdy footwear (over-the-ankle leather shoes or boots with low heels), leather gloves, jeans and a long-sleeved shirt or jacket, Nyman said.

Staying alert on a motorcycle is also critical. Said Morris: "Teaching someone how to keep a motorcycle up in a straight line is easy. But teaching someone how to ride safely involves a lot of mental skills."

Based on studies of motorcycle accidents, experts advise riders to use a mental checklist to make quick decisions in traffic. The list includes scanning the scene to identify potential hazards, predicting where collisions might occur, deciding on evasive action and executing a decision.

Motorcyclists should also ride where they are most visible. "Wear bright clothing and choose the correct lane position," said Morris. "The left third of the lane is good most of the time because it puts you directly in the line of sight of car drivers."

This is particularly important since the USC study found that "the failure of motorists to detect and recognize motorcycles in traffic is the predominating cause of motorcycle accidents."

Even the advocates of motorcycle safety courses agree that training is not the solution to safety, but should help minimize the chances of injury.

"Motorcycle safety is a contradiction in terms," said Dr. Prudence Kline, assistant professor of emergency medicine at George Washington University Hospital. "No matter how careful you are and no matter how cautious and sober you are, in the event of somebody else's error, you have virtually no protection that you would in the shell of a car."