WASHINGTON — Just because you can talk to your car doesn’t mean you should. Two new studies have found that voice-activated smartphones and dashboard infotainment systems may be making the distracted-driving problem worse instead of better.

The systems let drivers do things like tune the radio, send a text message, or make a phone call while keeping their eyes on the road and their hands on the wheel, but many of these systems are so error-prone or complex that they require more concentration from drivers rather than less, according to studies released Tuesday by the AAA Foundation for Traffic Safety and the University of Utah.

One study examined infotainment systems in some of the most common auto brands on the road: Chevrolet, Chrysler, Ford, Hyundai and Mercedes. The second study tested the Apple iPhone’s Siri voice system to navigate, send texts, make Facebook and Twitter posts, and use the calendar without handling or looking at the phone. Apple and Google are working with automakers to mesh smartphones with infotainment systems so that drivers can bring their apps, navigation and music files into their cars.

The voice-activated systems were graded on a distraction scale of 1 to 5, with 1 representing no distraction and 5 comparable to doing complex math problems and word memorization.

The systems were tested by 162 university students and other volunteers in three settings: a laboratory, a driving simulator and in cars while driving through a Salt Lake City neighborhood.

Apple’s Siri received the worst rating, 4.14. Two times, test drivers using Siri in a driving simulator rear-ended another car.

Chevrolet’s MyLink received the worst rating, 3.7, among the infotainment systems. Infotainment systems from three other automakers – Mercedes, Ford and Chrysler – also were rated more distracting for drivers than simply talking on a handheld cellphone. Most of the cars were 2013 model year vehicles.

“What we continue to see from customers is that they demand this level of technology in their vehicles, that access to music and access to calls is now a critical part of the driving experience and so we’re looking at innovative ways to provide that,” said Chevrolet spokeswoman Annalisa Bluhm.

The systems with the worst ratings were those that made errors even though drivers’ voice commands were clear and distinct, said Strayer. Drivers had to concentrate on exactly what words they wanted to use and in what order to get the systems to follow their commands, creating a great deal of frustration.

For example, an infotainment system might recognize a command to change a radio station to “103.5 FM,” but not “FM 103.5” or simply “103.5,” he said.

The studies contradict claims by automakers, who have been pitching the voice systems to car buyers as a way they can safely enjoy social media and connectivity.

“Infotainment systems are unregulated,” said Deborah Hersman, president of the National Safety Council and former chairman of the National Transportation Safety Board.

“It is like the Wild West, where the most critical safety feature in the vehicle – the driver – is being treated like a guinea pig in human trials with new technologies.”