DETROIT (AP) -- In the not-too-distant future, automatic emergency braking will have to come standard on all new passenger vehicles in the United States, a requirement that the government says will save hundreds of lives and prevent thousands of injuries every year.

The National Highway Traffic Safety Administration unveiled the final version of the new regulation on Monday and called it the most significant safety rule in the past two decades. It's designed to prevent many rear-end and pedestrian collisions and reduce the roughly 40,000 traffic deaths that happen each year.

"We're living through a crisis in roadway deaths," Transportation Secretary Pete Buttigieg said in an interview. "So we need to do something about it."

It's the U.S. government's first attempt to regulate automated driving functions and is likely to help curb some of the problems that have surfaced with driver-assist and fully automated driving systems.

Although about 90% of new vehicles have the automatic braking standard now under a voluntary agreement with automakers, at present there are no performance requirements, so some systems are may not be that effective. The new regulations set standards for vehicles to automatically stop and avoid hitting other vehicles or pedestrians, even at night.

"Part of how I think we're going to turn the corner on the unacceptable level of roadway deaths that we just lived with for my entire lifetime is through these kinds of technologies," said Buttigieg, who is 42. "We need to make sure we set high performance standards."

The regulation, which will require additional engineering to bolster software and possibly add hardware such as radar, won't go into effect for more than five years. That will give automakers time to bolster their systems during the normal model update cycle, NHTSA said.

It also will drive up prices, which NHTSA estimates at $354 million per year in 2020 dollars, or $82 per vehicle. But Buttigieg said it will save 362 lives per year, prevent about 24,000 injuries and save billions in property damage.

Critics say the standards should have come sooner, and that they don't appear to require that the systems spot people on bicycles, scooters or other vulnerable people.

The new rule requires all passenger vehicles weighing 10,000 pounds (4,500 kilograms) or less to have forward collision warning, automatic emergency braking and pedestrian detection braking.

The standards require vehicles to stop and avoid hitting a vehicle in front of them at speeds up to 62 miles per hour (100 kilometers per hour). Also they must apply the brakes automatically at up to 90 mph (145 kph) if a collision with vehicle ahead is imminent.

The systems also have to spot pedestrians during the day and night, and must stop and avoid a pedestrian at 31 mph to 40 mph (50 kph to 64 kph) depending on the pedestrian's location and movement.

The agency said that in 2019, nearly 2.2 million rear-end crashes were reported to police nationwide, killing 1,798 people and injuring 574,000 others. Sixty percent of fatal rear-end crashes and 73% of injury crashes were on roads with speed limits of 60 mph (97 kph) or below.

In addition, there were 6,272 pedestrians killed in crashes, with 65% of those people being hit by the front of a passenger vehicle.

The vast majority of deaths, injuries and property damage happens at speeds above 25 mph (40 kph), speeds that are not covered by the voluntary agreement, the agency said.

"Only regulation can ensure that all vehicles are equipped with AEB (automatic emergency braking) that meet minimum performance requirements," the regulation says.

NHTSA would conduct random tests to determine whether automakers are meeting the standards.

The agency said it isn't requiring what type of sensors each automaker must have to meet the requirements. That's up to the automakers. But in testing of 17 vehicles, only one -- a 2023 Toyota Corolla equipped with cameras and radar -- met the standards.

The regulation said radar would have to be added to about 5% of the systems in order to comply with the requirements.

Cathy Chase, president of Advocates for Highway and Auto Safety, said the new standards will make it clear to car buyers that AEB will work properly. Most consumers, she said, are unaware that there are no requirements in place now.

"By and large, it's better to have AEB than not have AEB," she said. "So once the AEB rule is put into place, once again the federal government will be doing its job and protecting consumers."

NHTSA said it changed its original proposal, giving automakers more than five years to meet the standards instead of three. Chase said shorter would be better.

"The shorter the timeline, the more people are going to be saved, the quicker these are going to get into cars and our roadways are going to be safer for everyone," she said.

Chase said she is not pleased that the rule does not appear to include standards for bicyclists or people using scooters.