The AAA, a U.S. consumer and travel services organization, said the tests illustrate how current assisted driving and automated braking systems fall short of true autonomous driving, and require drivers to stay in control of vehicles.

A fast-growing number of new vehicles are equipped with Automated Driver Assistance Systems, or ADAS, that partially automate functions such as steering, staying in a lane and braking. Tesla's Autopilot is one of the best-known such systems, but most major automakers offer similar technology. Regulators, auto insurers and automakers warn that ADAS systems cannot safely substitute for a human driver's full attention.

In their latest study of the limitations of assisted driving technology, researchers for AAA set up four scenarios for the three tested models: Overtaking a dummy car traveling in the same direction as the tested vehicle; overtaking a dummy cyclist heading in the same direction; confronting a dummy car on a head-on collision course at 25 miles per hour; and avoiding a dummy bicycle rider crossing the test car's path.

All three tested vehicles detected and avoided hitting the dummy vehicles and cyclists traveling in the same direction, ahead of the tested vehicles, AAA said.

But the Hyundai Santa Fe and Subaru Forester did not appear to detect or slow to avoid colliding with the foam dummy vehicle during a simulated head-on collision, AAA said.

The Model 3 did automatically hit its brakes when it detected the oncoming dummy car, slowing to 3.2 miles per hour or slower before colliding with the dummy car.

Tesla did not reply with comments on the study. Hyundai said in a statement it "is reviewing the findings in AAA's report as part of our ongoing commitment to customer safety."

Subaru is looking into the AAA test to understand the methodology and does not have a detailed response at this time, spokesman Dominick Infante said in an email. The automaker has improved its EyeSight assisted driving system for the 2022 model year Forester, he added.

AAA said a Subaru Forester it tested failed to detect a simulated bicycle rider crossing its path in five test runs. A Tesla Model 3 and a Hyundai Santa Fe did see and brake for a dummy cyclist crossing their paths.

(Reporting By Joe White; Editing by Nick Zieminski)

By Joseph White