When Susan E. Cameron's Corvette collided with Bernard O. Short's Dodge pickup near Front Royal this fall, Short was slammed into his steering wheel, injuring his chest. Cameron, whose 8-month-old son was with her in the Corvette, suffered a collapsed lung and several cracked ribs, police said.

The crash on state Route 522 demolished both vehicles, but young William Cameron emerged from the wreck unscathed. The reason: When the crash occurred, he was safely strapped into his child-restraint seat.

Virginia state police and top officials in the state's Department of Transportation Safety discuss that Sept. 23 crash with relish, for in that one accident, they say, lies the beauty of a new state law requiring parents who drive with infants to secure them in approved safety seats.

"It's a terrific, real-world accident that shows exactly what the child-restraint law is all about," said David O. McAllister, a member of a three-man team which investigated that crash and others involving children around the state. "That child would have been seriously injured or killed if he hadn't been in that seat."

The new law, which takes effect on Saturday, caps several years of work by McAllister and other highway safety experts to reduce infant injuries in car accidents, the leading killer and crippler of children in the country. Passed by the 1982 General Assembly, the law makes Virginia the 19th state to have enacted such legislation. Tennessee, which approved a similar law four years ago, was the first.

The law applies to parents driving with their own children younger than 4 years old, and grants some limited exemptions. Infants who weigh more than 40 pounds, for instance, may be secured in car safety belts; physicians may exempt children whose size or physical condition make using the seat impractical, but the parent must carry the exemption when driving with the child.

Additionally, the child safety seats must be approved by the state police and violations for not securing a child or placing it in an unapproved seat carry maximum $25 fines. Fines collected under the law will be used to replenish the state's 2,000-seat loan pool, officials said.

"We've been trying to get this law passed in Virginia for the past five to eight years," said McAllister, "but the attitude and climate has never been right for it.

"Some people argued that it was taking away their freedom, that government was telling them what do," McAllister said. "Now, that may be true, but the child in that car has no decision. That's what the law is about: protecting the child.

"This law is long overdue."

Nearly 650 children died last year in car accidents nationwide, and more than 5,000 were permanently disabled or seriously injured in car accidents, according to the National Transportation Safety Board, which earlier this month called on other states without child-seat laws to enact such legislation promptly. Twelve of the fatalities were in Virginia, the department reported.

Ruth Robertson, the spokeswoman of the state's Department of Transportation Safety, said 400 to 500 people already have applied for the seats under the law's poverty provisions. Those unable to buy the seats, which can cost as much as $50, may apply for them under income guidelines similar to those used by state and federal welfare agencies.

In Northern Virginia, two hospitals are offering new parents approved seats at little or no cost. Alexandria Hospital loans the seats at no charge for a child's first car ride home; the seats usually are returned within a week.

Arlington Hospital's loan program makes safety seats avaliable for a $5 refundable deposit and a charge of $6 for six months. A spokeswoman said 18 seats have been rented since Dec. 8.

A spokeswoman for Fairfax Hospital said officials there now are considering similar loan programs.

McAllister, who has been investigating car accidents involving children for the past 11 years, said a Richmond woman's car flipped over last winter with a child inside.

"She was doing only about 20 miles per hour, but she hit an icy patch and her small foreign car flipped right over," he recalled.

The woman was shaken up in the accident, McAllister said. But her napping baby, strapped in its safety seat, slept through the entire incident.