New research suggests voice-activated phone apps can distract drivers even more than handheld or hands-free phone use. (LM Otero/Associated Press)

Voice-activated applications that let drivers keep their hands on the wheel were supposed to be an antidote to distracted driving, but research into the cause of 3,300 traffic deaths and 420,000 injuries each year says such systems can actually be a significant distraction.

The applications can be more distracting than either handheld or hands-free cellphone use, according to research presented Tuesday by the AAA Foundation for Traffic Safety.

Now available in almost all new vehicles, the apps let drivers speak commands to make calls, send text messages, change music selections, enter GPS destinations and control interior temperature. The more complex and error-prone systems frustrated and distracted drivers.

“As workload goes up, cognitive distraction goes up,” said the foundation’s president, Peter Kis­singer. “That suppresses brain activity, it slows reaction time and it decreases visual scanning and we start missing cues in the driving process, and all of that increases risk of a crash.”

The foundation’s research is not the first to delve into how the brain responds to different challenges while the driver attempts to negotiate traffic, but it is among the first to examine the applications devised to address distracted driving.

Half a dozen years ago, as concern grew about distracted driving, research on the topic was in its nascent stage. But since then the studies have piled to a lofty stack, and virtually all of them have drawn a similar conclusion: Safe driving requires strict attention to the road. Distractions of any sort put people at risk.

The AAA Foundation study, the second in as many years, is among the most sophisticated to date to document the cause of various levels of distraction. Last year’s research laid the groundwork, concluding that voice-based systems “may have unintended consequences that adversely affect traffic safety.”

The report released Tuesday confirmed that with tests of the level of distraction caused by several factory-installed voice systems and the popular Siri system offered on Apple iPhones.

It used a relatively simply grading system. Level 1 was minimal distraction — listening to the radio or audiobooks. Level 2 was moderate distraction — talking on a handheld or hands-free cellphone. Levels 3 and 4 were a high level of distraction.

The foundation’s 2013 research already had determined that voice-activated applications rated a hair above Level 3, while hands-free conversation was closer to Level 2 and handheld ranked between 2 and 3. (Talking to a passenger came in at about 2.4, audiobooks fell at about 1.8, and listening to the radio was 1.2)

The iPhone’s Siri ranked above Level 4.

“This likely reflects the added complexity when the voice-recognition system is less than perfect,” the report said. “Common issues involved inconsistencies in which Siri would produce different responses to seemingly identical commands. In other circumstances, Siri required exact phrases to accomplish specific tasks and subtle deviations from that phrasing would result in a failure.”

Kissinger said his researchers talked with Apple technicians before they began testing.

“We tested the kind of things that they said their customers were demanding,” he said. “For the functionality that we tested — texting, updating Facebook, tweeting and checking your calendar — we saw a very high level of cognitive distraction.”

Kissinger said Siri and some factory-installed systems demanded too much attention from drivers, often because they required a high level of precision in delivering commands.

“For example, if you’re trying to tune the radio and you want to dial 103.5, you can almost say anything that says 103.5, it’ll understand it,” he said. “Whereas in some systems the only correct thing you can say is ‘103.5 FM.’ The driver gets very frustrated with that, and before you know it, is much more engaged in that act than they should be.

Kissinger said the wife of his research director “was trying to change the radio one day and instead she changed the temperature in the car. She wanted to go to 103.5 and she ended up with a temperature of 103.5.”

In evaluating systems by six automakers — Toyota, Hyundai, Chrysler, Mercedes, Ford and Chevrolet — the researchers found that Toyota and Hyundai generally were less distracting to use while Mercedes and Chevrolet were at the other end of the spectrum.

“The blueprint for success is one in which systems are simple, easy to use, intuitive, error-free and minimize time on task,” Kissinger said. “Where we saw systems that were not necessarily intuitive, where there was error in translation, where the person had difficulty talking to the system and understanding what the system was doing, we saw drivers get frustrated, the workload went up, and the cognitive distraction went up.”

Given the thousands of annual deaths and hundreds of thousands of crash injuries, Kissinger said, drivers and automakers should work to minimize distractions.

“These risks are real,” he said. “For car manufacturers, we’re asking them to be informed by these research findings and to design systems that are simple and intuitive and as error-free as possible to minimize time on task.”