Newer automatic emergency braking systems prevent about twice the number of crashes that older models do but still fail to stop crashes at high speeds, a challenge for automakers preparing to meet a strict new federal standard for the technology.

Model-year 2024 vehicles with automatic emergency braking avoided 100 percentof forward collisions at 35 mph, a much better performance than 2017 and 2018vehicles, which avoided collisions 51percent of the time at that speed, according to research published Oct. 24 by AAA.

“AAA is very pleased to find that automatic emergency braking systems are getting significantly better, and that’s a great result for drivers and safety of the road,” said Greg Brannon, director of automotive research at AAA.

However, only three out of four test vehicles were able to avoid a collision at 45 mph, and none could avoid a collision at 55 mph.

NHTSA is requiring that all new vehicles be equipped with automatic emergency braking that can meet a high-speed requirement starting in September 2029. Vehicles must avoid a collision automatically with no manual braking for speeds of up to 50 mph. Vehicles must avoid a collision at speeds of up to 62.2 mph when a combination of the automatic emergency brake and the manual brake is engaged.

While AAA tested only full automatic emergency braking without driver intervention, that none of the vehicles could avoid a collision at 55 mph suggests that the industry has a ways to go to meet the new federal standard.

“The new standard doesn’t go into place until 2029, so there’s a lot of work and development and testing and things that will have to happen between now and then,” Brannon said. “The good news is, we’ve got five years to do that.”

Automatic emergency braking has well-documented safety benefits, but the technology must navigate complexity. The government has determined that automatic emergency braking must prevent crashes at certain speeds, but oversensitivity of the system can pose its own danger.

Manufacturers including Honda, General Motors, Mazda, Nissan, Tesla and Volkswagen have faced investigations or recalls related to false activations of the systems, when vehicles brake for nonexistent obstacles. NHTSA has compiled reports of injuries because of these false activations — 93, for example, as a part of the Honda investigation. And automakers and other stakeholders have voiced concerns that stricter standards could create more false positives.

Despite the challenges facing manufacturers that must meet the new standard, the AAA research indicates that in seven years, automakers have been able to double the prevention capabilities of their automatic emergency braking systems.

The automotive industry has been “tuning, refining and making better, and the tweaking of those those algorithms combined with the additional sensors — it seems to be headed in the right direction,” Brannon said.