Pedestrians are displayed on the video display of a backup camera on a Toyota Prius in San Francisco.

New cars sold in the U.S. must now have backup cameras to help drivers avoid accidents.

A federal regulation took full effect Wednesday requiring the rearview cameras and video displays on new models.

Safety advocates say the cameras will help prevent accidents in which pedestrians — often children — are run over because a driver can't see them.

Congress passed a law in 2008 requiring regulators to enact measures requiring the adoption of technology to greatly improve rearview visibility.

After years of delays, the U.S. Department of Transportation announced the camera requirement in 2014, giving automakers several years to prepare.

Many higher-end models and mainstream vehicles with extra safety packages already have rearview cameras. But the technology will now be standard in even the cheapest of new cars.

"The regulation is a monumental advancement of safety for children, pedestrians, bicyclists and other vulnerable road users," said Cathy Chase, president of Advocates for Highway and Auto Safety, in a statement.

Backover crashes kill more than 200 people annually and injure more than 12,000.

More from USA Today:

Tesla accused of violating Nikola Motor patents with electric semi truck, sues for $2B

Ford kills the Taurus, Fiesta and Fusion: What we loved and hated about the cars

Nissan sales plunge, Ford, others also down in April as auto industry cools off