Cars being sold in the United States must come equipped with a backup camera by May 2018.

Federal safety regulators finalized a rule requiring the installation of rear-view cameras Monday morning after years of delays. They believe the law will reduce the number of pedestrians killed each year when they are accidentally backed over.

Roughly 200 people are killed and 14,000 are injured in such accidents every year in the United States, and slightly less than half the victims are children under age five too small to be seen from the driver's seat. A government analysis has shown that about half of the victims could have been saved by a backup camera.

Safety advocates hailed the finalization of the standards Monday, which came one day before the US Court of Appeals for the Second Circuit was scheduled to hear a lawsuit brought by safety groups seeking to compel a final ruling in a years-long process.

"This has been such a fight," said Janette Fennell, the president and founder of KidsAndCars.org, a nonprofit organization that advocates for safer vehicles for children. "But we're ecstatic to hear the news."

It has been a bruising battle. Congress passed legislation requiring the adoption of a rear-view visibility standard in 2007. President George W. Bush signed the "Cameron Gulbransen Kids Transportation Safety Act" into law. It required the National Highway Traffic Safety Administration to issue specific standards by 2011. But officials delayed the deadline for writing those rules five separate times. In December, several organizations filed a lawsuit to force NHTSA to release the rules.

"As a father, I can only imagine how heart-wrenching these types of accidents can be for families," said US Department of Transportation Secretary Anthony Foxx. "We hope that today's rule will serve as a significant step toward reducing these tragic accidents."

The rules apply to all vehicles that weigh less than 10,000 pounds, including trucks and buses. Cameras must show a field of view that encompasses a 10-foot by 20-foot zone directly behind the vehicle.

Data shows that backup cameras have already been popular with consumers. They're included on slightly less than half all new models sold today, and a NHTSA analysis concluded they'd be available on 73 percent of all vehicles covered by the rule by 2018 anyway.

The same analysis found that equipping a car with a backup camera would cost $43 to $45 per vehicle in a car already equipped with a visual display, and $132 to $142 for vehicles without one.

Critics of the legislation have said that the cost of enacting the law will tally between $700 million and 1.6 billion, a cost that will be passed along to car shoppers. With NHTSA reportedly employing a statistical cost of $6.1 million as the financial worth of a human life, this legislation is expected to cost between $11.8 million and $19.7 million per life saved.

Yet NHTSA's analysis doesn't discount the "emotional cost" of accidentally killing children is something that lies outside the scope of its normal cost-benefit analysis:

"The agency recognizes that most people place a high value on the lives of children and that there is a general consensus regarding the need to protect children as they are unable to protect themselves," the report said. "As backover-crash victims are often struck by their immediate family members or caretakers, it is the Department's opinion that an exceptionally high emotional cost, not easily convertible to monetary equivalents, is often inflicted upon the familes of backover crash victims."

Fennell, who has worked with many families involved in backover injuries and deaths, said the grieving parents often feel like they're the only ones to ever experience such an accident. But they often grow angry when they realize that an average of 50 such accidents are reported every week, but no standards have been reached to prevent them. Now, those standards exist.

"These are not accidents," Fennell said. "These are predictable, preventable tragedies."